Full light reflection presentation. Total light reflection

In this lesson, you will become familiar with the phenomenon of light refraction and learn how light travels through different environments.

Lesson plan:

• 1. .
• 2. Limiting angle of total reflection. Law of total reflection.
• 3. Limiting angle of total reflection for some environments.
• 4. Fiber optics. Light guide
• 5. Reflective prisms.
• 6. Conclusions.

• When switching from optical less dense medium V optically more tight refraction angle less perpendicular .
• When switching from optical more dense medium V optically less tight refraction angle more angle of incidence and the beam of refraction is deflected towards interface between two media .

When switching from optical more dense medium V optically less dense, the refracted ray of light is deflected towards the interface between two Wednesdays from its original direction .

42º - this is the angle at which a ray of light from glass does not pass into the second medium, but is completely reflected

Limit angle of reflection

Sin γ

Sin α ̥

n

n

2

1

= ─

n = 1

Sin90º = 1

1

γ = 90º

─ limit angle

α

total reflection

0

Sin α ̥ = ─

n

─ Law of complete

reflections

2

Limit angle of total reflection

• Lowest angle of incidence α , at which the phenomenon of total reflection of light occurs is called maximum angle of full reflections .

• For the angle of total reflection, the condition is satisfied - the sine of the angle of total reflection is inversely proportional to the relative refractive index of light.

0

0

Sin α ̥ = ─

n

3. Limit angle of reflection and refractive index n for some environments

Wednesday

Limit angle of reflection

Water (at 20 ºС)

48º35′ ≈ 48º

Glass

41º50′ ≈ 42º

Quartz

Ruby

Diamond

24º40′ ≈ 24º

4. Fiber optics

• It is based on the transmission of light and images through bundles of transparent flexible fibers - light guides.
• Light guide - this is a thin fiber cylindrical made of quartz glass with the addition of germanium or boron.
• The thickness of the fibers is from 100 microns to 1 microns and less.
• The fibers are collected into bundles with up to a million fibers.

fiber cable

used for transmission

• information inside a computer and for connecting different computers with each other;
• television images.

Light guide

Due to multiple total reflections, light can be directed along any curved path.

Reflective

prisms

Conclusion:

Total reflection is observed

• when light passes from optical more dense medium V optically less dense;
• when the angle of incidence reaches the limiting angle of total reflection.

Law of total reflection -

The sine of the angle of total reflection is inversely proportional to the relative refractive index of light.

n

Sin α ̥ = ─

α). When light passes from an optically denser medium to a less dense medium, light is both refracted and reflected. As the angle of incidence α increases, the angle of refraction also increases β (β>α). When light passes from an optically denser medium to a less dense medium, light" class="link_thumb"> 5 !} When light passes from an optically denser medium to a less dense medium, the light is both refracted and reflected. As the angle of incidence α increases, the angle of refraction β also increases (β>α). When light passes from an optically denser medium to a less dense medium, the light is both refracted and reflected. As the angle of incidence α increases, the angle of refraction β also increases (β>α). At a certain angle of incidence α o the angle of refraction becomes greatest (β max =90 o). At a certain angle of incidence α o the angle of refraction becomes greatest (β max =90 o). If the angle of incidence α>α о, the refraction of light into the second medium stops, the light is completely reflected from the interface, as from a mirror - the phenomenon of total reflection of light occurs. If the angle of incidence α>α о, the refraction of light into the second medium stops, the light is completely reflected from the interface, as from a mirror - the phenomenon of total reflection of light occurs. α). When light passes from an optically denser medium to a less dense medium, light as n"> α). When light passes from an optically denser medium to a less dense medium, the light is both refracted and reflected. As the angle of incidence α increases, the angle of refraction β increases (β >α). At a certain angle of incidence α o the angle of refraction becomes greatest (β max =90 o). At a certain angle of incidence α o the angle of refraction becomes greatest (β max =90 o). If the angle of incidence α>α o, the refraction of light. into the second medium stops, the light is completely reflected from the interface, as from a mirror - the phenomenon of total reflection of light occurs. If the angle of incidence α>α o, the refraction of light into the second medium stops, the light is completely reflected from the interface, like from a mirror - the phenomenon arises. total reflection of light."> α). When light passes from an optically denser medium to a less dense medium, light is both refracted and reflected. As the angle of incidence α increases, the angle of refraction also increases β (β>α). When light passes from an optically denser medium to a less dense medium, light"> title="When light passes from an optically denser medium to a less dense one, the light is both refracted and reflected. As the angle of incidence α increases, the angle of refraction β also increases (β>α). When light passes from an optically denser medium to a less dense medium, light as"> !}

Fiber optics - a system for transmitting optical images; a system for transmitting optical images using glass fibers (light guides). using glass fibers (light guides). Experiencing total internal reflection, the light signal propagates inside the flexible light guide Experiencing total internal reflection, the light signal propagates inside the flexible light guide A bundle of thousands of light guides is used (the diameter of each fiber is from 0.002 to 0.01 mm) A beam of thousands of light guides is used (the diameter of each fiber is from 0.002 up to 0.01 mm) The use of fiber-optic devices in medicine - endoscopes (probes inserted into various internal organs) The use of fiber-optic devices in medicine - endoscopes (probes inserted into various internal organs) Currently, fiber optics is replacing metal conductors in information transmission systems (using a light signal, you can transmit 10 6 times more information than using a radio signal) Currently, fiber optics is replacing metal conductors in information transmission systems (using a light signal, you can transmit 10 6 times more information than using a radio signal) using a radio signal) Use of total reflection in prismatic binoculars, periscopes, SLR cameras, reflectors (reflectors) Use of total reflection in prismatic binoculars, periscopes, SLR cameras, reflectors (reflectors)

Slide 1

Seminar on the topic: “Light waves” Total reflection
Prepared by: Students of class 11 “A” Romanchenko Valeria, Shchipanova Elena, Filippova Alena.

Slide 2

Short story
Even the ancient Roman scientist Pliny, in his “Natural History,” written about 2 thousand years ago, talked about pearl divers who took olive oil into their mouths before diving and released it under water. An oil film spreading over the surface of the sea, the refractive index of which was greater than that of water, sharply reduced the brightness of the glare and improved visibility conditions.

The simple phenomenon of total internal reflection, first described by Johannes Kepler at the beginning of the 17th century and seemingly well studied, has now become the object of close attention.

And these effects were first studied by the Russian physicist Alexander Alexandrovich Eikhenwald exactly more than a hundred years ago.
Slide 3

Total reflection

- this is the phenomenon of reflection of light from an optically less dense medium, in which there is no refraction of light, and the intensity of the reflected light is almost equal to the intensity of the incident light.
Since light passes from an optically denser medium to an optically less dense medium, the angle of refraction in this case is greater than the angle of incidence a.

As the angle of incidence of rays from the source on the interface between two media increases, a moment will come when the refracted ray will go along the interface between the media, that is = 90°. The angle of incidence corresponding to this value is called the limiting angle of total internal reflection - a0.

Slide 5

The limiting angle of total reflection is the angle of incidence at which light is not refracted, but is reflected and slides along the interface between two media. Angle of refraction = 90°

Slide 6

Total reflection is used in so-called fiber optics to transmit light and images through bundles of transparent flexible fibers - light guides. The light guide is a cylindrical glass fiber coated with a sheath of transparent material with a lower refractive index than the fiber. Due to multiple total reflection, light can be directed along any path (straight or curved).

Slide 7

The fibers are gathered into bundles. In this case, each of the fibers transmits some element of the image. Bundles of fibers are used, for example, in medicine to study internal organs. As the technology for manufacturing long bundles of fibers - light guides - improves, communication (including television) using light rays is beginning to be used more and more widely.

Slide 8

Slide 9
PRACTICE
talks about phenomena in nature associated with the complete reflection of light.

Total internal reflection can be observed if you look from under water at the surface: at certain angles at the interface, it is not the outer part that is observed, but a mirror reflection of objects that are in the water.

Slide 10

2. The phenomenon of mirage is explained by a complete internal phenomenon. A mirage is an optical phenomenon in the atmosphere: the reflection of light by a boundary between layers of air that are sharply different in heat. For an observer, such a reflection means that together with a distant object, its virtual image is visible, shifted relative to the object.

Slide 11

3.Rainbow. Most often, a primary rainbow is observed, in which the light undergoes one internal reflection. In a primary rainbow, the red color is on the outside of the arc, its angular radius is 40–42°.

4. A complex optical phenomenon in the atmosphere, consisting of several forms of mirages, in which distant objects are visible repeatedly and with various distortions. Fatamorgana occurs when several alternating layers of air of varying densities are formed in the lower layers of the atmosphere, capable of giving specular reflections. As a result of reflection, as well as refraction of rays, real-life objects produce several distorted images on the horizon or above it, partially overlapping each other and quickly changing in time, which creates a bizarre picture.

Slide 13

How to explain the “game of stones”? In jewelry, the cut of stones is selected so that there is a complete reflection of light on each face.

Slide 14

periscope
binoculars
movie camera

Slide 15

Slide 16

New achievements
At first, complete reflection was only a curious phenomenon. Now it is gradually leading to revolution.

Charles Kao was awarded the 2009 Nobel Prize in Physics for his “pioneering achievements in the transmission of light through fibers for optical communications.” Kao's discovery, which he made in 1966, paved the way for optical fibers, which are used today in television and Internet communications. He was able to develop a method for producing ultra-pure optical fiber, making it possible to transmit light signals without distortion over distances of up to 100 km, compared to only tens of meters, which was the limit at that time.

Slide 17
Presentation “Total reflection of light”. Gordon G.V. Geometric optics. http://www.rusedu.ru/detail_6171.html Borisov K. Fiber optic lighting systems. http://www.trikita.by/service6.html Bukhovtsev B.B., Myakishev G.Ya. Physics textbook 11th grade. M.: Education. 2010 Varaksina E. I. Total internal reflection of light in a liquid. http://fiz.1september.ru/articles/2009/17/14. Kasyanov V.A. Physics textbook 11th grade. M.:Drofa.2002 Latyshevskaya T. Yu., Novoselov K. S. Nanotechnologies for Fiber Optics. http://www.kabel-news.ru/ http://traditio.ru/wiki/ Internal reflection http://hghltd.yandex.net/. Total reflection of light http://ru.wikipedia.org/wiki/Light guide http://images.google.ru. Mirages http://school426-spb.by.ru. Fata Morgana http://www.genon.ru/GetAnswer. Photos http://www.universal-fibre-optics.com/russian/applications.html. Fiber optic lighting systems http://www.ifmo.ru/faculty/5. Unique robotic complex http://www.forc-photonics.ru/ru/production/volokonno-opticheskie_datchik/1/68/.Optical instruments http://optika8.narod.ru/Opiti.htm. Geometric optics http://canegor.urc.ac.ru/bezpriborov/63832896.html. Experiments demonstrating total internal reflection of light http://www.nvtc.ee/e-oppe/Sidorova/objects. Application of total internal reflection of light. http://iuyt.ru/index.php?newsid=38. Lighting design http://dic.academic.ru/dic.nsf/bse/144040/ Fata Morgana