نور شناسی

معنی کلمه نور شناسی

معنی واژه نور شناسی

معنیرش به: ناوبری, جستجو

نورشناسی، اپتیک یا فیزیک نور، شاخه‌ای از فیزیک است که به بررسی نور و خواص آن و برهمکنش آن با ماده می‌پردازد. نورشناسی به مطالعه حوزه مرئی، ماواء بنفش و زیر قرمز امواج الکترومغناطیسی می‌پردازد.
محتویات


* ۱ تاریخچه
* ۲ نورشناسی هندسی
* ۳ نورشناسی موجی
* ۴ نورشناسی کوانتمی
* ۵ منبع

تاریخچه

ابن هیثم که به پدر علم نورشناسی نیز موسوم است از اولین کسانی است که به مطالعه نور پرداخت.
نورشناسی هندسی

نورشناسی هندسی نور به صورت یک پرتو منتشر شونده در یک خط راست مدل بندی می‌کند. این نظریه توانسته‌است بسیاری از ویژگی‌های نور مثل شکست نور، بازتاب نور از سطوح را به خوبی توصیف نماید.
نورشناسی موجی

پدیده‌هایی وجود دارند که دیگر نمی‌توان آنها را با دید نور هندسی مورد مطالعه قرار داد که نمونه‌ای از این پدیده‌ها پراش، پاشندگی، تداخل نور می‌باشد. به این منظور با کارهای ماکسول مشخص شد که رفتار نور به خوبی با استفاده از یک موج الکترومغناطیسی قابل توصیف است.
نورشناسی کوانتمی
جستجو در ویکی‌انبار در ویکی‌انبار پرونده‌هایی دربارهٔ نورشناسی موجود است.

با وجود همه موفقیت‌هایی که در زمینه نورشناسی انجام شده بود باز هم هنوز نور ماهیت اصلی خود را هویدا نکرده بود. اما با پیشرفت‌هایی که در زمینه مکانیک کوانتومی انجام شد و کاربرد آن در حوزه نورشناسی جبهه‌های جدیدی در این علم گشوده و نمودهای تازه‌ای از نور مشاهده شد. این موضوع تا جایی ادامه یافت که اعتقاد دانشمندان فیزیک بر آن شد که نور ذاتا یک موجود کاملا کوانتمی است و آنچه که در تئوری‌های کلاسیک به آن پرداخته می‌شود یک تقریب نسبتا خوب از نور است. در این مدل بندی جدید پدیده‌هایی پیش بینی و توصیف شدند که پیش از این بررسی نمی‌شدند. امروزه موفق‌ترین مدل برای توصیف نور مدل نورشناسی کوانتومی است.
منبع

1. ↑ نورشناسی از واژه‌های مصوب فرهنگستان زبان و ادب فارسی به جای optics در انگلیسی است. «فرهنگ واژه‌های مصوّب فرهنگستان: ۱۳۷۶ تا ۱۳۸۵». فرهنگستان زبان و ادب فارسی. بازبینی‌شده در ۲۹ اسفند ۱۳۹۰.

Driggers, Ronald G. (ed.) (۲۰۰۳). Encyclopedia of Optical Engineering. New York: Marcel Dekker. 3 vols.
نماد خرد این یک نوشتار خُرد پیرامون فیزیک است. با گسترش آن به ویکی‌پدیا کمک کنید.
ن • ب • و
برگرفته از «
رده‌های صفحه:

* فیزیک نور
از ویکی پدیا
قس عربی
یصف عِلْم البَصَریاتِ أو المَناظِرِ سلوک الطیف المرئی، تحت الأحمر، فوق البنفسجی، بشکل مجمل معظم الأمواج الکهرطیسیة والظواهر المشابهة مثل الأشعة السینیة، الأمواج المیکرویة microwave، الأمواج الرادیویة وغیرها من أنواع الأمواج والإشعاع الکهرطیسی. لذا یتم اعتبار البصریات أحیانا فرعا من الکهرطیسیة. تعتمد بعض الظواهر البصریة على میکانیکا الکم لکن الغالبیة العظمى من الظواهر البصریة یمکن شرحها وتفسیرها بناء على الوصف الکهرطیسی للضوء الذی تحدده بدقة قوانین ماکسویل.

بشکل کبیر تعتبر البصریات حقل دراسی مستقل عن بقیة فروع واختصاصات الفیزیاء بحیث یملک کیانا مستقلا وجمعیات علمیة خاصة ومؤتمرات خاصة، تدعى النواحی العلمیة البحتة من البصریات فیزیاء بصریة optical physics اما النواحی التطبیقیة فتدعى هندسة بصریة optical engineering.

تاریخیاً یعتبر العالم العربی ابن الهیثم 965-1039 م مؤسس علم بصریات بکتابه الفرید المناظر، وهو الذی قام بتوصیف آلیة الابصار العین کجسم مستقبل للضوء فحسب، مخالفاً نظریة بطلیموس الذی اقترح أن العین تصدر الضوء أیضاً.

أهم تطبیقات علم البصریات الیوم فی المجال التکنولوجیا هی الألیاف البصریة لنقل البیانات وأشعة اللیزر.

البصریات هی العلم الذی یتعامل مع الضوء فی کیفیه تولده وانتشاره اما الضوء فهو نوع من أنواع الطاقات المعروفة کالطاقة الحراریه والطاقة المیکانیکیه والطاقة الکهربیه ولکن الطاقة الضوئیة تظهر فی صورة خاصه من صور الطاقة هی الصورة الاشعاعیة والتی تؤثر فی العین فتسبب الرؤیة وتتحول هذه الطاقة الاشعاعیة الضوئیة إلى الأنواع المعروفة للطاقة تحقیقا لمبدأ بقاء الطاقة وکیفیة رؤیة العین لا کما کان یفسر قدیما بأن الأشعة تخرج من العین فتسقط على الجسم فترى العین ویعرف الضوء المرئی بأنه الاشعاع الذی یؤثمر فی العین فیسبب الرؤیة وتعتمد درجة وضوح رؤیة الجسم المرئی على الکم والنوع للطاقه المرتدة من الجسم والتی تستقبلها العین وکل نقطة على الجسم المرئی تعتبر مصدرا للاشعاع تستقبل منه العین کل الأشعة الصادرة منه على شکل مخروطى قاعدته هی العین وقمته هی النقطة التی على الجسم المضئ. ینتشر الضوء فی جمیع الاتجاهات بسرعة فائقة جدا لدرجة انه لا یوجد فی تجاربنا الیومیه ما یدعونا للظن بإن سرعة الضوء لیست نهائیة وتقل سرعة الضوء فی الأوساط المادیة فمثلا سرعة الضوء فی الماء أکبر من سرعته فی الماس. و تختلف مصادر الضوء عن بعضها فی مقدار الذبذبات الصادرة منها وبذلک تختلف فی مقدار الطاقة الاضعاعیة الصادرة عنها وبالتالى تأثیرها على الرؤیه أی انها تختلف فی طول الموجة والتردد ویتضح من هذا علاقه الألوان المکونة للضوء کل واحد منها له طول موجى وتردد خاصین بها ویختلفان عن باقى الألوان. أوضح ماکسویل ان الضوء هو أحد الأجزاء المکونة للطیف الکهرومغناطیسى
محتویات


* 1 الضوء المرئى
* 2 مواضیع البصریات التقلیدیة
* 3 مواضیع البصریات الحدیثة
* 4 حقول البصریات الأخرى
* 5 انظر أیضا
o 5.1 جمعیات

الضوء المرئى

یمکن تعریف هذا المدى من طیف الموجات الکهرطیسیه بإنه ذلک الطیف الذی یمکن أن یؤثر فی العین فی العین فتحس الرؤیه ویبدأ المدى باللون البنفسجى وینتهى یاللون الأحمر ونظرا لان حساسیه العین تختلف باختلاف طول موجه الأشعة الضوئیة المستقبلة فهی قادره على التمییز بین الألوان المختلفة وتکون حساسیه العین أکبر ما یمکن عند الطول الموجى الذی یقع بین الأخضر والاصفر وتقاس اطوال الموجات الضوئیة بوحدات صغیره جدا مثل المیکرومتر والنانومتر والانجستروم.
مواضیع البصریات التقلیدیة
رسوم متحرکة توضح مفهوم تشتت الضوء فی المنشور

* الزیغ
* التماسک
* الانحراف
* التفرق
* تشویه
* وتصنیع واختبار (العناصر البصریة)
* مبدأ فرمات
* بصریات فورییه
* متدرجة مؤشر بصریات
* عدسة البصریة وتصمیم
* البصریة القرار
* الاستقطاب
* رای (البصریات)
* تتبع رای
* التأمل
* الانکسار
* التبعثر
* موجة

* البصریات الهندسیة :
o عدسات
o المرایات
o صناعة العدسات
o الموشورات

مواضیع البصریات الحدیثة

* Adaptive optics
* Circular dichroism
* Crystal optics
* Diffractive optics
* Guided wave optics
* Holography
* Integrated optics
* Jones calculus
* Lasers
* Micro-optics
* Non-imaging optics
* Nonlinear optics
* Optical modeling and simulation methods
* Optical pattern recognition
* Optical processors
* Photometry
* Photonics
* Quantum optics
* Radiometry
* Statistical optics
* Stray light
* Thin-film optics
* X-ray optics

حقول البصریات الأخرى

* Color science
* Illumination engineering
* Image processing
* Information theory
* Linear optics
* Machine vision
* Materials science - optical properties
* Optical communication
* Optical computers
* Optical data storage
* Optical display system
* Optical feedback
* Pattern recognition
* Photography (science of)
* Thermal physics — radiative heat transfer
* Visual system

انظر أیضا
Portal-puzzle.svg بوابة الفیزیاء

* List of optical topics
* Important publications in optics
* Transparency (optics)
* History of optics
* Optical illusion
* Optics is a book of Ptolemy
* Optician

جمعیات

* Optical Society of America
* SPIE — The International Society for Optical Engineering
* European Optical Society

مشاریع شقیقة هناک المزید من الصور والملفات فی ویکیمیدیا کومنز حول: بصریات

ع • ن • ت
الفروع العامة فی الفیزیاء
عزل الصوت • فیزیاء زراعیة • فیزیاء فلکیة • فیزیاء الغلاف الجوی • فیزیاء ذریة وجزیئیة وبصریة • فیزیاء حیویة • فیزیاء کیمیائیة • فیزیاء المواد المکثفة • دینامیکا (دینامیکا الموائع • دینامیکا حراریة) • فیزیاء اقتصادیة • کهرومغناطیسیة (بصریات • کهرباء • مغناطیسیة) • فیزیاء الأرض • فیزیاء ریاضیة • میکانیکا (میکانیکا کلاسیکیة • میکانیکا الکم • میکانیکا إحصائیة) • فیزیاء طبیة • ماوراء الطبیعة • فیزیاء عصبیة • فیزیاء نوویة • فیزیاء الجسیمات • نظریة الحقل الکمومی • النسبیة (النسبیة الخاصة • النسبیة العامة) • فیزیاء التربة • علم السکون (علم سکون الموائع)
تم الاسترجاع من "
تصنیفان:

* فروع الفیزیاء
* بصریات
قس آذزبایجانی
Optika (qəd. yun. ὀπτική „Görüənlər haqında elm“, optiko „Görməyə aid“, opsis „Görmək“) fizikanın bir sahəsi olub, işığın yaranması, xassəsləri, təbiəti və həmçinin ətraf mühitdə baş verən optik fenomenləri öyrənir. Optikaya həm də işıq haqqında elm deyilir. İşıq dedikdə təkcə gözlə görünənişıq yox, həm də ona yaxın olan böyük spekt nəzərədə tutulur.

Elektromaqnit spekt radiodalğalara, infraqırmızı, görünən, ultrabənövşəyi, rentgen və qamma şüalarına bölürlər. Bu spektr sahələri təkcə təbiətləri ilə deyil, həm də şüalanmanın yaranması və qəbul etmək qabiliyyətinə görə fərqlənirlər. Buna görə də, işıq spektrləri arasında dəqiq keçid yoxdur, sərhədlər isə şərtidir.

Dalğa və kvant qanunauyğunluqları elektromaqnit şüalanmalarının spektrləri üçün ümumi sayılırlar. Yalnız dalğa uzunluğundan asılı oaraq müxtəlif hadisələr, üsullar və praktiki tətbiq sahələri ön plana çıxır.Ona görə də, optikaya yalnız ayrılıqda götürülümş bir spketrik öyürənilməsini həyata keçirən qapalı sahə kimi baxmaq olmaz. Bu və ya digər spektr sahəsi üçün əldə edilmiş qanunuyğunluq başqa spektrlər üçün də tətbiq oluna bilər.

Optikanın məşğul olduğu sahələrə aşağıdakılar aiddirlər:

* Həndəsi optika
* Dalğa optikası
* Təbiətdə dalğa optikası
* Lazer fizikası (koherent optika)
* Qeyri-xətti optika
* Kvant optikası
* Qradiyent optikası


g • m • r
Optikanın bölmələri
Əsas istiqamətlər Dalğa optikası • Fiziki optika • Fizioloji optika • Fotometriya • Həndəsi optika • İşığın buraxılması nəzəriyyəsi • İşığın maddə ilə qarşılıqlı təsir nəzəriyyəsi • Kvant optikası • Qeyri-xətti optika • Lazer optikası • Optik cihazlar • Optoelektronika • Spektroskopiya
Qarışıq istiqamətlər Akustooptika • Kristallooptika

Bu məqalənin azərbaycan dili əlifbasının ərəb qrafikası ilə qarşılığı vardır. Bax: اوپتیک
ترکی استانبولی
* Fiziğin optik olarak adlandırılan kısmı ışığın davranışını inceler. Işığın uzayda izlediği yolu inceleyen optiğe geometrik optik diyoruz. Geometrik optiğin içinde de kırınım, girişim ve yansıma-kırılma olayları bulunmaktadır. Önce basit olan olaydan başlarsak; yansıma ve kırılma günlük hayatta çıplak gözle görülebilen olaylardır. Örneğin, yarısı su ile doldurulmuş bir bardağın içine bir çubuk koyarsak çubuğu bir doğru şeklinde göremeyiz. Bunun nedeni ışığın kırılma indisleri farklı bir ortamdan diğerine geçmesidir. sin a_{1} cdot n_{1} = sin a_{2} cdot n_{2} Snell Yasası ile ifade edilir.


Girişim olayı üst üste binme ya da yok etme ile sonuçlanır. Girişim yapan dalgalar arasındaki faz farkı 180 derece ise ve dalga boyları eşit ise son dalga genliği iki kat artar. Eğer 0 derece ise birbirlerini yok ederler.

Kırınım olayı bir dalganın engellere çarparak kenarlarından bükülmesidir. Herhangi bir yarıktan geçen dalga d sin a=+lambda kadar yol alır. (burada x geçen dalganın dalgaboyudur.)

Girişim, kırınım ve kutuplanma (polarizasyon) olayları ışığın dalga yapısını desteklerken fotoelektrik olay, Compton olayı ve kara cisim ışıması ışığın tanecikli yapıda olduğunu gösterir. Işık çift karakterli olup, hem dalga hem de tanecik özelliği taşır.

g • t • d
Teknoloji
Uygulamalı Bilim
Kazıbilim • Yapay zekâ • Bilgisayarcılık • Elektronik • Enerji • Enerji depolama • Mühendislik jeofiziği • Mühendislik jeolojisi • Çevre teknolojisi • Balıkçılık bilimi • Malzeme bilimi • Mikroteknoloji • Mimarlık • Nanoteknoloji • Nükleer teknoloji • Optik • Parçacık fiziği • Zoografi
Bilgi
İletişim teknolojisi • Grafik tekniği • Bilgi teknolojisi • Müzik teknolojisi • Ses tanıma • Görsel teknolojiler • Sistematik • Bilişim
Endüstri
Yapı • Mali mühendislik • Balıkçılık • Endüstriyel teknoloji • Üretim • Makine • Madencilik •
Askeri
Cephane • Bomba • Muharebe mühendisliği • Askeri teknoloji •
Ev
Eğitim teknolojisi • • Eviçi teknolojileri • Gıda teknolojisi
Mühendislik
Bilgisayar mühendisliği • Biyokimya mühendisliği • Biyomedikal mühendisliği • Biyoteknoloji • Cevher hazırlama mühendisliği • Çevre mühendisliği • Deri mühendisliği • Deniz teknolojisi mühendisliği • Elektrik mühendisliği • Elektronik mühendisliği • Elektrik ve elektronik mühendisliği • Elektronik ve haberleşme mühendisliği • Endüstri mühendisliği • Fizik mühendisliği • Gemi inşaatı ve gemi makineleri mühendisliği • Gemi makineleri işletme mühendisliği • Genetik mühendisliği • Gıda mühendisliği • Harita mühendisliği • Havacılık ve uzay mühendisliği • İnşaat mühendisliği • İşletme mühendisliği • Jeofizik Mühendisliği • Jeoloji mühendisliği • Kimya mühendisliği • Kontrol mühendisliği • Makine mühendisliği • Maden mühendisliği • Matematik mühendisliği • Mekatronik mühendisliği • Metalurji ve malzeme mühendisliği • Meteoroloji mühendisliği • Mücevherat Mühendisliği • Nükleer enerji mühendisliği • Petrol ve doğalgaz mühendisliği • Peyzaj mimarlığı • Orman mühendisliği • Otomotiv mühendisliği • Seramik mühendisliği • Ses mühendisliği • Tekstil mühendisliği • Telekomünikasyon mühendisliği • Uçak mühendisliği • Uzay mühendisliği • Üretim mühendisliği • Yazılım mühendisliği • Ziraat mühendisliği
Sağlık / Güvenlik
Biyomedikal • Biyokimya • Biyoinformatik • Biyoteknoloji • Kemoinformatik • Yangın önleme mühendisliği • Sağlık bilimi • Medikal teknoloji • Beslenme • Eczacılık • Güvenlik mühendisliği • Hijyen mühendisliği
Ulaşım
Havacılık • Motorlu taşıtlar • Uzay teknolojisi
" adresinden alındı.
Kategori:

* Optik
* Peyzaj mimarlığı
قس انگلیسی
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties.

Most optical phenomena can be accounted for using the classical electromagnetic description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice. Practical optics is usually done using simplified models. The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces. Physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be accounted for in geometric optics. Historically, the ray-based model of light was developed first, followed by the wave model of light. Progress in electromagnetic theory in the 19th century led to the discovery that light waves were in fact electromagnetic radiation.

Some phenomena depend on the fact that light has both wave-like and particle-like properties. Explanation of these effects requires quantum mechanics. When considering lights particle-like properties, the light is modeled as a collection of particles called "photons". Quantum optics deals with the application of quantum mechanics to optical systems.

Optical science is relevant to and studied in many related disciplines including astronomy, various engineering fields, photography, and medicine (particularly ophthalmology and optometry). Practical applications of optics are found in a variety of technologies and everyday objects, including mirrors, lenses, telescopes, microscopes, lasers, and fiber optics.
Contents


* 1 History
* 2 Classical optics
o 2.1 Geometrical optics
+ 2.1.1 Approximations
+ 2.1.2 Reflections
+ 2.1.3 Refractions
o 2.2 Physical optics
+ 2.2.1 Modelling and design of optical systems using physical optics
+ 2.2.2 Superposition and interference
+ 2.2.3 Diffraction and optical resolution
+ 2.2.4 Dispersion and scattering
+ 2.2.5 Polarization
* 3 Modern optics
o 3.1 Lasers
* 4 Applications
o 4.1 Human eye
+ 4.1.1 Visual effects
+ 4.1.2 Optical instruments
o 4.2 Photography
o 4.3 Atmospheric optics
* 5 See also
* 6 References
* 7 External links

History
Main article: History of optics
See also: Timeline of electromagnetism and classical optics
The Nimrud lens

Optics began with the development of lenses by the ancient Egyptians and Mesopotamians. The earliest known lenses were made from polished crystal, often quartz, and have been dated as early as 700 BC for Assyrian lenses such as the Layard/Nimrud lens. The ancient Romans and Greeks filled glass spheres with water to make lenses. These practical developments were followed by the development of theories of light and vision by ancient Greek and Indian philosophers, and the development of geometrical optics in the Greco-Roman world. The word optics comes from the ancient Greek word ὀπτική, meaning appearance or look.

Greek philosophy on optics broke down into two opposing theories on how vision worked, the "intro-mission theory" and the "emission theory". The intro-mission approach saw vision as coming from objects casting off copies of themselves (called eidola) that were captured by the eye. With many propagators including Democritus, Epicurus, Aristotle, Galen and their followers, this theory seems to have some contact with modern theories of what vision really is, but it remained only speculation lacking any experimental foundation.

Plato first articulated the emission theory, the idea that visual perception is accomplished by rays emitted by the eyes. He also commented on the parity reversal of mirrors in Timaeus. Some hundred years later, Euclid wrote a treatise entitled Optics where he linked vision to geometry, creating geometrical optics. He based his work on Platos emission theory wherein he described the mathematical rules of perspective and describes the effects of refraction qualitatively, although he questioned that a beam of light from the eye could instantaneously light up the stars every time someone blinked. Ptolemy, in his treatise Optics, held an extramission-intromission theory of vision: the rays (or flux) from the eye formed a cone, the vertex being within the eye, and the base defining the visual field. The rays were sensitive, and conveyed information back to the observer’s intellect about the distance and orientation of surfaces. He summarized much of Euclid and went on to describe a way to measure the angle of refraction, though he failed to notice the empirical relationship between it and the angle of incidence.
Reproduction of a page of Ibn Sahls manuscript showing his knowledge of the law of refraction, now known as Snells law

During the Middle Ages, Greek ideas about optics were resurrected and extended by writers in the Muslim world. One of the earliest of these was Al-Kindi (c. 801–73) who wrote on the merits of Aristotelian and Euclidean ideas of optics, favoring the emission theory since it could better quantify optical phenomenon. In 984, the Persian mathematician Ibn Sahl wrote the treatise "On burning mirrors and lenses", correctly describing a law of refraction equivalent to Snells law. He used this law to compute optimum shapes for lenses and curved mirrors. In the early 11th century, Alhazen (Ibn al-Haytham) wrote the Book of Optics (Kitab al-manazir) in which he explored reflection and refraction and proposed a new system for explaining vision and light based on observation and experiment. He rejected the "emission theory" of Ptolemaic optics with its rays be emitted by the eye, and instead put forward the idea that light reflected in all directions in straight lines from all points of the objects being viewed and then entered the eye, although he was unable to explain the correct mechanism of how the eye captured the rays. Alhazens work was largely ignored in the Arabic world but it was anonymously translated into Latin around 1200 A.D. and further summarized and expanded on by the polish monk Witelo making it a standard text on optics in Europe for the next 400 years.

In the 13th century medieval Europe the English bishop, Robert Grosseteste wrote on a wide range of scientific topics discussing light from four different perspectives: an epistemology of light, a metaphysics or cosmogony of light, an etiology or physics of light, and a theology of light, basing it on the works Aristotle and Platonism. Grossetestes most famous disciple, Roger Bacon, wrote works citing a wide range of recently translated optical and philosophical works, including those of Alhazen, Aristotle, Avicenna, Averroes, Euclid, al-Kindi, Ptolemy, Tideus, and Constantine the African. Bacon was able to use parts of glass spheres as magnifying glasses to demonstrate that light reflects from objects rather than being released from them.

In Italy, around 1284, Salvino DArmate invented the first wearable eyeglasses. This was the start of the optical industry of grinding and polishing lenses for these "spectacles", first in Venice and Florence in the thirteenth century, and later in the spectacle making centers in both the Netherlands and Germany. Spectacle makers created improved types of lenses for the correction of vision based more on empirical knowledge gained from observing the effects of the lenses rather than using the rudimentary optical theory of the day (theory which for the most part could not even adequately explain how spectacles worked). This practical development, mastery, and experimentation with lenses led directly to the invention of the compound optical microscope around 1595, and the refracting telescope in 1608, both of which appeared in the spectacle making centers in the Netherlands.

In the early 17th century Johannes Kepler expanded on geometric optics in his writings, covering lenses, reflection by flat and curved mirrors, the principles of pinhole cameras, inverse-square law governing the intensity of light, and the optical explanations of astronomical phenomena such as lunar and solar eclipses and astronomical parallax. He was also able to correctly deduce the role of the retina as the actual organ that recorded images, finally being able to scientifically quantify the effects of different types of lenses that spectacle makers had been observing over the previous 300 years. After the invention of the telescope Kepler set out the theoretical basis on how they worked and described an improved version, known as the Keplerian telescope, using two convex lenses to produce higher magnification.
Cover of the first edition of Newtons Opticks

Optical theory progressed in the mid-17th century with treatises written by philosopher René Descartes, which explained a variety of optical phenomena including reflection and refraction by assuming that light was emitted by objects which produced it. This differed substantively from the ancient Greek emission theory. In the late 1660s and early 1670s, Newton expanded Descartes ideas into a corpuscle theory of light, famously showing that white light, instead of being a unique color, was really a composite of different colors that can be separated into a spectrum with a prism. In 1690, Christian Huygens proposed a wave theory for light based on suggestions that had been made by Robert Hooke in 1664. Hooke himself publicly criticized Newtons theories of light and the feud between the two lasted until Hookes death. In 1704, Newton published Opticks and, at the time, partly because of his success in other areas of physics, he was generally considered to be the victor in the debate over the nature of light.

Newtonian optics was generally accepted until the early 19th century when Thomas Young and Augustin-Jean Fresnel conducted experiments on the interference of light that firmly established lights wave nature. Youngs famous double slit experiment showed that light followed the law of superposition, which is a wave-like property not predicted by Newtons corpuscle theory. This work led to a theory of diffraction for light and opened an entire area of study in physical optics. Wave optics was successfully unified with electromagnetic theory by James Clerk Maxwell in the 1860s.

The next development in optical theory came in 1899 when Max Planck correctly modeled blackbody radiation by assuming that the exchange of energy between light and matter only occurred in discrete amounts he called quanta. In 1905, Albert Einstein published the theory of the photoelectric effect that firmly established the quantization of light itself. In 1913, Niels Bohr showed that atoms could only emit discrete amounts of energy, thus explaining the discrete lines seen in emission and absorption spectra. The understanding of the interaction between light and matter, which followed from these developments, not only formed the basis of quantum optics but also was crucial for the development of quantum mechanics as a whole. The ultimate culmination was the theory of quantum electrodynamics, which explains all optics and electromagnetic processes in general as being the result of the exchange of real and virtual photons.

Quantum optics gained practical importance with the invention of the maser in 1953 and the laser in 1960. Following the work of Paul Dirac in quantum field theory, George Sudarshan, Roy J. Glauber, and Leonard Mandel applied quantum theory to the electromagnetic field in the 1950s and 1960s to gain a more detailed understanding of photodetection and the statistics of light.
Classical optics

Classical optics is divided into two main branches: geometrical optics and physical optics. In geometrical, or ray optics, light is considered to travel in straight lines, and in physical, or wave optics, light is considered to be an electromagnetic wave.

Geometrical optics can be viewed as an approximation of physical optics which can be applied when the wavelength of the light used is much smaller than the size of the optical elements or system being modelled.
Geometrical optics
Main article: Geometrical optics
Geometry of reflection and refraction of light rays

Geometrical optics, or ray optics, describes the propagation of light in terms of "rays" which travel in straight lines, and whose paths are governed by the laws of reflection and refraction at interfaces between different media. These laws were discovered empirically as far back as 984 AD and have been used in the design of optical components and instruments from then until the present day. They can be summarised as follows:

When a ray of light hits the boundary between two transparent materials, it is divided into a reflected and a refracted ray.

The law of reflection says that the reflected ray lies in the plane of incidence, and the angle of reflection equals the angle of incidence.

The law of refraction says that the refracted ray lies in the plane of incidence, and the sine of the angle of refraction divided by the sine of the angle of incidence is a constant.

frac {sin { heta_1}}{sin { heta_2}} = n

where n is a constant for any two materials and a given colour of light. It is known as the refractive index.

The laws of reflection and refraction can be derived from Fermats principle which states that the path taken between two points by a ray of light is the path that can be traversed in the least time.
Approximations

Geometric optics is often simplified by making the paraxial approximation, or "small angle approximation." The mathematical behavior then becomes linear, allowing optical components and systems to be described by simple matrices. This leads to the techniques of Gaussian optics and paraxial ray tracing, which are used to find basic properties of optical systems, such as approximate image and object positions and magnifications.
Reflections
Main article: Reflection (physics)
Diagram of specular reflection

Reflections can be divided into two types: specular reflection and diffuse reflection. Specular reflection describes the gloss of surfaces such as mirrors, which reflect light in a simple, predictable way. This allows for production of reflected images that can be associated with an actual (real) or extrapolated (virtual) location in space. Diffuse reflection describes opaque, non limpid materials, such as paper or rock. The reflections from these surfaces can only be described statistically, with the exact distribution of the reflected light depending on the microscopic structure of the material. Many diffuse reflectors are described or can be approximated by Lamberts cosine law, which describes surfaces that have equal luminance when viewed from any angle. Glossy surfaces can give both specular and diffuse reflection.

In specular reflection, the direction of the reflected ray is determined by the angle the incident ray makes with the surface normal, a line perpendicular to the surface at the point where the ray hits. The incident and reflected rays and the normal lie in a single plane, and the angle between the reflected ray and the surface normal is the same as that between the incident ray and the normal. This is known as the Law of Reflection.

For flat mirrors, the law of reflection implies that images of objects are upright and the same distance behind the mirror as the objects are in front of the mirror. The image size is the same as the object size. The law also implies that mirror images are parity inverted, which we perceive as a left-right inversion. Images formed from reflection in two (or any even number of) mirrors are not parity inverted. Corner reflectors retroreflect light, producing reflected rays that travel back in the direction from which the incident rays came.

Mirrors with curved surfaces can be modeled by ray-tracing and using the law of reflection at each point on the surface. For mirrors with parabolic surfaces, parallel rays incident on the mirror produce reflected rays that converge at a common focus. Other curved surfaces may also focus light, but with aberrations due to the diverging shape causing the focus to be smeared out in space. In particular, spherical mirrors exhibit spherical aberration. Curved mirrors can form images with magnification greater than or less than one, and the magnification can be negative, indicating that the image is inverted. An upright image formed by reflection in a mirror is always virtual, while an inverted image is real and can be projected onto a screen.
Refractions
Main article: Refraction
Illustration of Snells Law for the case n1 n2, such as air/water interface

Refraction occurs when light travels through an area of space that has a changing index of refraction; this principle allows for lenses and the focusing of light. The simplest case of refraction occurs when there is an interface between a uniform medium with index of refraction n_1 and another medium with index of refraction n_2. In such situations, Snells Law describes the resulting deflection of the light ray:

n_1sin heta_1 = n_2sin heta_2

where heta_1 and heta_2 are the angles between the normal (to the interface) and the incident and refracted waves, respectively. This phenomenon is also associated with a changing speed of light as seen from the definition of index of refraction provided above which implies:

v_1sin heta_2 = v_2sin heta_1

where v_1 and v_2 are the wave velocities through the respective media.

Various consequences of Snells Law include the fact that for light rays traveling from a material with a high index of refraction to a material with a low index of refraction, it is possible for the interaction with the interface to result in zero transmission. This phenomenon is called total internal reflection and allows for fiber optics technology. As light signals travel down a fiber optic cable, it undergoes total internal reflection allowing for essentially no light lost over the length of the cable. It is also possible to produce polarized light rays using a combination of reflection and refraction: When a refracted ray and the reflected ray form a right angle, the reflected ray has the property of "plane polarization". The angle of incidence required for such a scenario is known as Brewsters angle.

Snells Law can be used to predict the deflection of light rays as they pass through "linear media" as long as the indexes of refraction and the geometry of the media are known. For example, the propagation of light through a prism results in the light ray being deflected depending on the shape and orientation of the prism. Additionally, since different frequencies of light have slightly different indexes of refraction in most materials, refraction can be used to produce dispersion spectra that appear as rainbows. The discovery of this phenomenon when passing light through a prism is famously attributed to Isaac Newton.

Some media have an index of refraction which varies gradually with position and, thus, light rays curve through the medium rather than travel in straight lines. This effect is what is responsible for mirages seen on hot days where the changing index of refraction of the air causes the light rays to bend creating the appearance of specular reflections in the distance (as if on the surface of a pool of water). Material that has a varying index of refraction is called a gradient-index (GRIN) material and has many useful properties used in modern optical scanning technologies including photocopiers and scanners. The phenomenon is studied in the field of gradient-index optics.
A ray tracing diagram for a converging lens.

A device which produces converging or diverging light rays due to refraction is known as a lens. Thin lenses produce focal points on either side that can be modeled using the lensmakers equation. In general, two types of lenses exist: convex lenses, which cause parallel light rays to converge, and concave lenses, which cause parallel light rays to diverge. The detailed prediction of how images are produced by these lenses can be made using ray-tracing similar to curved mirrors. Similarly to curved mirrors, thin lenses follow a simple equation that determines the location of the images given a particular focal length (f) and object distance (S_1):

frac{1}{S_1} + frac{1}{S_2} = frac{1}{f}

where S_2 is the distance associated with the image and is considered by convention to be negative if on the same side of the lens as the object and positive if on the opposite side of the lens. The focal length f is considered negative for concave lenses.
Lens1.svg

Incoming parallel rays are focused by a convex lens into an inverted real image one focal length from the lens, on the far side of the lens. Rays from an object at finite distance are focused further from the lens than the focal distance; the closer the object is to the lens, the further the image is from the lens. With concave lenses, incoming parallel rays diverge after going through the lens, in such a way that they seem to have originated at an upright virtual image one focal length from the lens, on the same side of the lens that the parallel rays are approaching on. Rays from an object at finite distance are associated with a virtual image that is closer to the lens than the focal length, and on the same side of the lens as the object. The closer the object is to the lens, the closer the virtual image is to the lens.

Likewise, the magnification of a lens is given by

M = - frac{S_2}{S_1} = frac{f}{f - S_1}

where the negative sign is given, by convention, to indicate an upright object for positive values and an inverted object for negative values. Similar to mirrors, upright images produced by single lenses are virtual while inverted images are real.

Lenses suffer from aberrations that distort images and focal points. These are due to both to geometrical imperfections and due to the changing index of refraction for different wavelengths of light (chromatic aberration).
Images of black letters in a thin convex lens of focal length f are shown in red. Selected rays are shown for letters E, I and K in blue, green and orange, respectively. Note that E (at 2f) has an equal-size, real and inverted image; I (at f) has its image at infinity; and K (at f/2) has a double-size, virtual and upright image.
Physical optics
Main article: Physical optics

In physical optics, light is considered to propagate as a wave. This model predicts phenomena such as interference and diffraction, which are not explained by geometric optics. The speed of light waves in air is approximately 3.0×108 m/s (exactly 299,792,458 m/s in vacuum). The wavelength of visible light waves varies between 400 and 700 nm, but the term "light" is also often applied to infrared (0.7–300 μm) and ultraviolet radiation (10–400 nm).

The wave model can be used to make predictions about how an optical system will behave without requiring an explanation of what is "waving" in what medium. Until the middle of the 19th century, most physicists believed in an "ethereal" medium in which the light disturbance propagated. The existence of electromagnetic waves was predicted in 1865 by Maxwells equations. These waves propagate at the speed of light and have varying electric and magnetic fields which are orthogonal to one another, and also to the direction of propagation of the waves. Light waves are now generally treated as electromagnetic waves except when quantum mechanical effects have to be considered.
Modelling and design of optical systems using physical optics

Many simplifed approximations are available for analysing and designing optical systems. Most of these use a single scalar quantity to represent the electric field of the light wave, rather than using a vector model with orthogonal electric and magnetic vectors. The Huygens–Fresnel equation is one such model. This was derived empirically by Fresnel in 1815, based on Huygens hypothesis that each point on a wavefront generates a secondary spherical wavefront, which Fresnel combined with the principle of superposition of waves. The Kirchoff diffraction equation, which is derived using Maxwells equations, puts the Huygens-Fresnel equation on a firmer physical foundation. Examples of the application of Huygens–Fresnel principle can be found in the sections on diffraction and Fraunhofer diffraction.

More rigorous models, involving the modelling of both electric and magnetic fields of the light wave, are required when dealing with the detailed interaction of light with materials where the interaction depends on their electric and magnetic properties. For instance, the behaviour of a light wave interacting with a metal surface is quite different from what happens when it interacts with a di-electric material. A vector model must also be used to model polarized light.

Numerical modeling techniques such as the finite element method, the boundary element method and the transmission-line matrix method can be used to model the propagation of light in systems which cannot be solved analytically. Such models are computationally demanding and are normally only used to solve small-scale problems that require accuracy beyond that which can be achieved with analytical solutions.

All of the results from geometrical optics can be recovered using the techniques of Fourier optics which apply many of the same mathematical and analytical techniques used in acoustic engineering and signal processing.

Gaussian beam propagation is a simple paraxial physical optics model for the propagation of coherent radiation such as laser beams. This technique partially accounts for diffraction, allowing accurate calculations of the rate at which a laser beam expands with distance, and the minimum size to which the beam can be focused. Gaussian beam propagation thus bridges the gap between geometric and physical optics.
Superposition and interference
Main articles: Superposition principle and Interference (optics)

In the absence of nonlinear effects, the superposition principle can be used to predict the shape of interacting waveforms through the simple addition of the disturbances. This interaction of waves to produce a resulting pattern is generally termed "interference" and can result in a variety of outcomes. If two waves of the same wavelength and frequency are in phase, both the wave crests and wave troughs align. This results in constructive interference and an increase in the amplitude of the wave, which for light is associated with a brightening of the waveform in that location. Alternatively, if the two waves of the same wavelength and frequency are out of phase, then the wave crests will align with wave troughs and vice-versa. This results in destructive interference and a decrease in the amplitude of the wave, which for light is associated with a dimming of the waveform at that location. See below for an illustration of this effect.
combined
waveform Interference of two waves.svg
wave 1
wave 2

Two waves in phase Two waves 180° out
of phase
When oil or fuel is spilled, colorful patterns are formed by thin-film interference.

Since the Huygens–Fresnel principle states that every point of a wavefront is associated with the production of a new disturbance, it is possible for a wavefront to interfere with itself constructively or destructively at different locations producing bright and dark fringes in regular and predictable patterns. Interferometry is the science of measuring these patterns, usually as a means of making precise determinations of distances or angular resolutions. The Michelson interferometer was a famous instrument which used interference effects to accurately measure the speed of light.

The appearance of thin films and coatings is directly affected by interference effects. Antireflective coatings use destructive interference to reduce the reflectivity of the surfaces they coat, and can be used to minimize glare and unwanted reflections. The simplest case is a single layer with thickness one-fourth the wavelength of incident light. The reflected wave from the top of the film and the reflected wave from the film/material interface are then exactly 180° out of phase, causing destructive interference. The waves are only exactly out of phase for one wavelength, which would typically be chosen to be near the center of the visible spectrum, around 550 nm. More complex designs using multiple layers can achieve low reflectivity over a broad band, or extremely low reflectivity at a single wavelength.

Constructive interference in thin films can create strong reflection of light in a range of wavelengths, which can be narrow or broad depending on the design of the coating. These films are used to make dielectric mirrors, interference filters, heat reflectors, and filters for color separation in color television cameras. This interference effect is also what causes the colorful rainbow patterns seen in oil slicks.
Diffraction and optical resolution
Main articles: Diffraction and Optical resolution
Diffraction on two slits separated by distance d. The bright fringes occur along lines where black lines intersect with black lines and white lines intersect with white lines. These fringes are separated by angle heta and are numbered as order n.

Diffraction is the process by which light interference is most commonly observed. The effect was first described in 1665 by Francesco Maria Grimaldi, who also coined the term from the Latin diffringere, to break into pieces. Later that century, Robert Hooke and Isaac Newton also described phenomena now known to be diffraction in Newtons rings while James Gregory recorded his observations of diffraction patterns from bird feathers.

The first physical optics model of diffraction that relied on the Huygens–Fresnel principle was developed in 1803 by Thomas Young in his interference experiments with the interference patterns of two closely spaced slits. Young showed that his results could only be explained if the two slits acted as two unique sources of waves rather than corpuscles. In 1815 and 1818, Augustin-Jean Fresnel firmly established the mathematics of how wave interference can account for diffraction.

The simplest physical models of diffraction use equations that describe the angular separation of light and dark fringes due to light of a particular wavelength (lambda). In general, the equation takes the form

m lambda = d sin heta

where d is the separation between two wavefront sources (in the case of Youngs experiments, it was two slits), heta is the angular separation between the central fringe and the mth order fringe, where the central maximum is m = 0.

This equation is modified slightly to take into account a variety of situations such as diffraction through a single gap, diffraction through multiple slits, or diffraction through a diffraction grating that contains a large number of slits at equal spacing. More complicated models of diffraction require working with the mathematics of Fresnel or Fraunhofer diffraction.

X-ray diffraction makes use of the fact that atoms in a crystal have regular spacing at distances that are on the order of one angstrom. To see diffraction patterns, x-rays with similar wavelengths to that spacing are passed through the crystal. Since crystals are three-dimensional objects rather than two-dimensional gratings, the associated diffraction pattern varies in two directions according to Bragg reflection, with the associated bright spots occurring in unique patterns and d being twice the spacing between atoms.

Diffraction effects limit the ability for an optical detector to optically resolve separate light sources. In general, light that is passing through an aperture will experience diffraction and the best images that can be created (as described in diffraction-limited optics) appear as a central spot with surrounding bright rings, separated by dark nulls; this pattern is known as an Airy pattern, and the central bright lobe as an Airy disk. The size of such a disk is given by

sin heta = 1.22 frac{lambda}{D}

where θ is the angular resolution, λ is the wavelength of the light, and D is the diameter of the lens aperture. If the angular separation of the two points is significantly less than the Airy disk angular radius, then the two points cannot be resolved in the image, but if their angular separation is much greater than this, distinct images of the two points are formed and they can therefore be resolved. Rayleigh defined the somewhat arbitrary "Rayleigh criterion" that two points whose angular separation is equal to the Airy disk radius (measured to first null, that is, to the first place where no light is seen) can be considered to be resolved. It can be seen that the greater the diameter of the lens or its aperture, the finer the resolution. Interferometry, with its ability to mimic extremely large baseline apertures, allows for the greatest angular resolution possible.

For astronomical imaging, the atmosphere prevents optimal resolution from being achieved in the visible spectrum due to the atmospheric scattering and dispersion which cause stars to twinkle. Astronomers refer to this effect as the quality of astronomical seeing. Techniques known as adaptive optics have been utilized to eliminate the atmospheric disruption of images and achieve results that approach the diffraction limit.
Dispersion and scattering
Main articles: Dispersion (optics) and Scattering
Conceptual animation of light dispersion through a prism. High frequency (blue) light is deflected the most, and low frequency (red) the least.

Refractive processes take place in the physical optics limit, where the wavelength of light is similar to other distances, as a kind of scattering. The simplest type of scattering is Thomson scattering which occurs when electromagnetic waves are deflected by single particles. In the limit of Thompson scattering, in which the wavelike nature of light is evident, light is dispersed independent of the frequency, in contrast to Compton scattering which is frequency-dependent and strictly a quantum mechanical process, involving the nature of light as particles. In a statistical sense, elastic scattering of light by numerous particles much smaller than the wavelength of the light is a process known as Rayleigh scattering while the similar process for scattering by particles that are similar or larger in wavelength is known as Mie scattering with the Tyndall effect being a commonly observed result. A small proportion of light scattering from atoms or molecules may undergo Raman scattering, wherein the frequency changes due to excitation of the atoms and molecules. Brillouin scattering occurs when the frequency of light changes due to local changes with time and movements of a dense material.

Dispersion occurs when different frequencies of light have different phase velocities, due either to material properties (material dispersion) or to the geometry of an optical waveguide (waveguide dispersion). The most familiar form of dispersion is a decrease in index of refraction with increasing wavelength, which is seen in most transparent materials. This is called "normal dispersion". It occurs in all dielectric materials, in wavelength ranges where the material does not absorb light. In wavelength ranges where a medium has significant absorption, the index of refraction can increase with wavelength. This is called "anomalous dispersion".

The separation of colors by a prism is an example of normal dispersion. At the surfaces of the prism, Snells law predicts that light incident at an angle θ to the normal will be refracted at an angle arcsin(sin (θ) / n) . Thus, blue light, with its higher refractive index, is bent more strongly than red light, resulting in the well-known rainbow pattern.
Dispersion: two sinusoids propagating at different speeds make a moving interference pattern. The red dot moves with the phase velocity, and the green dots propagate with the group velocity. In this case, the phase velocity is twice the group velocity. The red dot overtakes two green dots, when moving from the left to the right of the figure. In effect, the individual waves (which travel with the phase velocity) escape from the wave packet (which travels with the group velocity).

Material dispersion is often characterized by the Abbe number, which gives a simple measure of dispersion based on the index of refraction at three specific wavelengths. Waveguide dispersion is dependent on the propagation constant. Both kinds of dispersion cause changes in the group characteristics of the wave, the features of the wave packet that change with the same frequency as the amplitude of the electromagnetic wave. "Group velocity dispersion" manifests as a spreading-out of the signal "envelope" of the radiation and can be quantified with a group dispersion delay parameter:

D = frac{1}{v_g^2} frac{dv_g}{dlambda}

where v_g is the group velocity. For a uniform medium, the group velocity is

v_g = c left( n - lambda frac{dn}{dlambda} ight)^{-1}

where n is the index of refraction and c is the speed of light in a vacuum. This gives a simpler form for the dispersion delay parameter:

D = - frac{lambda}{c} , frac{d^2 n}{d lambda^2}.

If D is less than zero, the medium is said to have positive dispersion or normal dispersion. If D is greater than zero, the medium has negative dispersion. If a light pulse is propagated through a normally dispersive medium, the result is the higher frequency components slow down more than the lower frequency components. The pulse therefore becomes positively chirped, or up-chirped, increasing in frequency with time. This causes the spectrum coming out of a prism to appear with red light the least refracted and blue/violet light the most refracted. Conversely, if a pulse travels through an anomalously (negatively) dispersive medium, high frequency components travel faster than the lower ones, and the pulse becomes negatively chirped, or down-chirped, decreasing in frequency with time.

The result of group velocity dispersion, whether negative or positive, is ultimately temporal spreading of the pulse. This makes dispersion management extremely important in optical communications systems based on optical fibers, since if dispersion is too high, a group of pulses representing information will each spread in time and merge together, making it impossible to extract the signal.
Polarization
Main article: Polarization (waves)

Polarization is a general property of waves that describes the orientation of their oscillations. For transverse waves such as many electromagnetic waves, it describes the orientation of the oscillations in the plane perpendicular to the waves direction of travel. The oscillations may be oriented in a single direction (linear polarization), or the oscillation direction may rotate as the wave travels (circular or elliptical polarization). Circularly polarized waves can rotate rightward or leftward in the direction of travel, and which of those two rotations is present in a wave is called the waves chirality.

The typical way to consider polarization is to keep track of the orientation of the electric field vector as the electromagnetic wave propagates. The electric field vector of a plane wave may be arbitrarily divided into two perpendicular components labeled x and y (with z indicating the direction of travel). The shape traced out in the x-y plane by the electric field vector is a Lissajous figure that describes the polarization state. The following figures show some examples of the evolution of the electric field vector (blue), with time (the vertical axes), at a particular point in space, along with its x and y components (red/left and green/right), and the path traced by the vector in the plane (purple): The same evolution would occur when looking at the electric field at a particular time while evolving the point in space, along the direction opposite to propagation.
Linear polarization diagram
Linear
انگلیسیoptics, physology
مرتبطنورشناسی، فیزیک نور، علم روشنایی، علم بینایی