–2/”>a >DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN” “http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd”>
, in physics, complete reflection of a ray of Light within a medium such as water or glass from the surrounding surfaces back into the medium. The phenomenon occurs if the angle of incidence is greater than a certain limiting angle, called the critical angle. In general, total internal reflection takes place at the boundary between two transparent media when a ray of light in a medium of higher index of refraction approaches the other medium at an angle of incidence greater than the critical angle. For a water-air surface the critical angle is 48.5°. Because indices of refraction depend on wavelength, the critical angle (and hence the angle of total internal reflection) will vary slightly with wavelength and, therefore, with colour. At all angles less than the critical angle, both refraction and reflection occur in varying proportions.
Uses of total internal reflection in daily life
- is the operating principle of optical fibers, which are used in endoscopes and telecommunications.
- is the operating principle of automotive rain sensors, which control automatic windscreen/windshield wipers.
- Another application of total internal reflection is the spatial filtering of light.
- Prisms in binoculars use total internal reflection, rather than reflective coatings, to fold optical paths and show erect images.
- Some multi-touch screens use frustrated total internal reflection in combination with a camera and appropriate Software to pick up multiple targets.
- Gonioscopy employs total internal reflection to view the anatomical angle formed between the eye's cornea and iris.
- A gait analysis instrument, CatWalk XT, uses frustrated total internal reflection in combination with a high speed camera to capture and analyze footprints of laboratory rodents.
- Optical fingerprinting devices use frustrated total internal reflection in order to record an image of a person's fingerprint without the use of ink.
- A total internal reflection fluorescence Microscope uses the evanescent wave produced by TIR to excite fluorophores close to a surface. This is useful for the study of surface properties of biological samples.
- is the operating principle of LED Light Panels. This technology utilizes LGPs (Light Guide Plates) as the vehicle for transmitting light over large areas. By etching a grid pattern on the second surface of the LGP, frustrated total internal reflection occurs allowing the light to escape the LGP as visible illumination.
Lens: converging and diverging lens
Lens, in optics, piece of glass or other transparent substance that is used to form an image of an object by focusing rays of light from the object. A lens is a piece of transparent material, usually circular in shape, with two polished surfaces, either or both of which is curved and may be either convex (bulging) or concave (depressed). The curves are almost always spherical; i.e., the radius of curvature is constant. A lens has the valuable property of forming images of objects situated in front of it. Single lenses are used in eyeglasses, contact lenses, pocket magnifiers, projection condensers, signal lights, viewfinders, and on simple box cameras. More often a number of lenses made of different materials are combined together as a compound lens in a tube to permit the correction of aberrations. Compound lenses are used in such instruments as cameras, microscopes, and telescopes.
Converging Lens
A biconvex lens or a plano convex lens converges parallel light rays that enter on one side to a point on the axis on the other side of the lens. Hence, a biconvex or a plano convex lens is called a converging lens. The point where the rays actually converge is called the focus of the lens and the distance of the focus from the lens is called focal length of the lens.
Diverging lens
When a set of parallel rays enter a biconcave lens or a plano concave lens, it diverges the light rays on the other side of the lens. Hence, a biconcave or a plano concave lens is called a diverging lens. However these divergent rays give an impression that they emerge from a point on the axis at the same side of entry of the rays. It is a virtual point and not real. This point is called the focus and its distance from the lens is called focal length of the concave lens.
Focal length
Focal length, usually represented in millimeters (mm), is the basic description of a photographic lens. It is not a measurement of the actual length of a lens, but a calculation of an optical distance from the point where light rays converge to form a sharp image of an object to the digital sensor or 35mm film at the focal plane in the camera. The focal length of a lens is determined when the lens is focused at infinity.
Optical centre image formation by lens
When an object is placed between the principal focus and optical centre of a convex lens, then a parallel ray of light AO passes through the focus after refraction along the direction OX. while the other ray AC pass through the optical centre and goes straight without any deviation along the direction CY. But, in this case the two refracted light rays i.e. OX and CY are diverging away from one another, so these cannot intersect each other to form a real image on the right side of the convex lens. Thus, the refracted rays OX and CY are extended backward by dotted lines. On extending back, these rays appear to intersect at point A’. Hence, the image A’B’ formed in this case is a virtual image which is formed on the same side of the lens behind the object. Also the image formed is erect and highly enlarged.
,
Total internal reflection (TIR) is an optical phenomenon that occurs when light passes from a medium with a higher refractive index to a medium with a lower refractive index at an angle greater than a certain critical angle. At this angle, the light is completely reflected back into the first medium.
The critical angle is the angle of incidence at which total internal reflection occurs. It is calculated using the following formula:
$$\sin \theta_c = \frac{n_2}{n_1}$$
where $\theta_c$ is the critical angle, $n_1$ is the refractive index of the first medium, and $n_2$ is the refractive index of the second medium.
The refractive index of a medium is a measure of how much light bends when it passes from one medium to another. The refractive index of air is 1.0003, while the refractive index of water is 1.333. This means that light bends more when it passes from air to water than it does when it passes from water to air.
TIR is used in a variety of applications, including fiber optic cables, prisms, periscopes, and mirages.
Fiber optic cables are used to transmit light signals over long distances. The light signals are transmitted through a series of thin, flexible fibers made of glass or plastic. The fibers are so thin that they can be bent around corners, which makes them ideal for use in telecommunications.
Prisms are used to split white light into its component colors. A prism is a triangular piece of glass or plastic that has two flat surfaces and one curved surface. When white light passes through a prism, the different colors of light are refracted at different angles. This is because the different colors of light have different wavelengths. The shorter wavelengths of light, such as blue light, are refracted more than the longer wavelengths of light, such as red light. This is why we see a rainbow of colors when we look through a prism.
Periscopes are used to see over obstacles. A periscope is a tube with two mirrors at each end. The mirrors are angled so that the light from an object above the periscope is reflected down the tube and into the viewer’s eyes. This allows the viewer to see the object without having to raise their head above the obstacle.
Mirages are optical illusions that can be seen in hot, dry weather. A mirage is an image of an object that is actually located below the horizon. The mirage is caused by the Refraction Of Light as it passes through layers of air with different temperatures. The hot air near the ground is less dense than the cooler air above it. This causes the light to bend, and the image of the object to appear to be floating in the air.
Diamonds are a type of gemstone that is made of carbon. Diamonds are very hard and have a high refractive index. This means that they can reflect and refract light very well. This is why diamonds are often used in jewelry.
TIR is a fascinating phenomenon that has many practical applications. It is responsible for the beauty of rainbows and diamonds, and it is used in a variety of technologies, such as fiber optic cables and periscopes.
What is the law of reflection?
The law of reflection states that the angle of incidence is equal to the angle of reflection. The angle of incidence is the angle between the incoming ray and the normal, which is an imaginary line perpendicular to the surface. The angle of reflection is the angle between the outgoing ray and the normal.
What is refraction?
Refraction is the bending of light as it passes from one medium to another. The amount of refraction depends on the difference in the refractive indices of the two media. The refractive index is a measure of how much light bends when it passes from one medium to another.
What is a lens?
A lens is a piece of transparent material that bends light. Lenses can be used to focus light, to magnify objects, or to project images.
What is a mirror?
A mirror is a surface that reflects light. Mirrors can be used to see images, to reflect light, or to create illusions.
What is a prism?
A prism is a piece of transparent material that separates white light into its component colors. This is because different colors of light have different wavelengths, and the prism bends each color of light by a different amount.
What is a rainbow?
A rainbow is an optical and meteorological phenomenon that causes a spectrum of light to appear in the sky when the Sun shines onto droplets of moisture in the Earth’s Atmosphere. Rainbows can be full circles. However, the observer normally sees only an arc formed by illuminated droplets above the ground, and centered on a line from the Sun to the observer’s eye.
What is a mirage?
A mirage is an optical phenomenon that causes an image of distant objects to appear displaced from their true position. Mirages are most commonly seen in hot, dry regions, such as deserts. They can also be seen on hot roads and in the air above hot pavement.
What is a Fata Morgana?
A Fata Morgana is a complex form of superior mirage that is associated with temperature inversions in the Earth’s atmosphere. It is most commonly seen in polar regions, but can also be seen in other parts of the world, such as the Strait of Messina between Italy and Sicily.
What is a halo?
A halo is a ring of light that appears around the Sun or Moon. Halos are caused by the refraction and reflection of light by ice crystals in the atmosphere.
What is a sun dog?
A sun dog is a bright spot of light that appears on either side of the Sun. Sun dogs are caused by the refraction and reflection of light by ice crystals in the atmosphere.
What is a corona?
A corona is a ring of light that appears around the Sun during a total Solar Eclipse. The corona is caused by the Sun’s corona, which is the outermost layer of the Sun’s atmosphere.
What is an aurora?
An aurora is a natural light display in the sky. Auroras are caused by the collision of charged particles from the Sun with the Earth’s atmosphere.
What is a shooting star?
A shooting star is a meteor, which is a small piece of rock or Metal that enters the Earth’s atmosphere. When a meteor enters the atmosphere, it heats up and begins to glow. The meteor is visible as a streak of light across the sky.
What is a comet?
A comet is a small, icy body that orbits the Sun. Comets have long, thin tails that are made of dust and gas. The tails of comets point away from the Sun.
What is a meteor shower?
A meteor shower is an astronomical event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth’s atmosphere at extremely high speeds on parallel trajectories. Most meteors are smaller than a grain of sand, so they burn up and disintegrate before they can reach the Earth’s surface.
Sure, here are some MCQs about the topics of refraction, reflection, and Snell’s law:
When light travels from one medium to another, it bends. This is called refraction. What causes refraction?
(A) The change in speed of light as it passes from one medium to another.
(B) The change in wavelength of light as it passes from one medium to another.
(C) The change in frequency of light as it passes from one medium to another.
(D) The change in direction of light as it passes from one medium to another.When light reflects off of a surface, it bounces back. This is called reflection. What type of reflection occurs when light reflects off of a smooth surface?
(A) Regular reflection
(B) Diffuse reflection
(C) Total internal reflection
(D) None of the aboveSnell’s law states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant. What is this constant called?
(A) The refractive index
(B) The index of refraction
(C) The Snell constant
(D) The refraction constantThe refractive index of a medium is a measure of how much light bends when it passes from one medium to another. What is the refractive index of air?
(A) 1.00
(B) 1.33
(C) 1.52
(D) 2.42The refractive index of water is 1.33. This means that light bends by 33% when it passes from air to water. What is the angle of incidence if the angle of refraction is 45 degrees?
(A) 30 degrees
(B) 45 degrees
(C) 60 degrees
(D) 75 degreesTotal internal reflection occurs when light travels from a medium with a high refractive index to a medium with a low refractive index. What is the critical angle for total internal reflection?
(A) The angle of incidence at which the angle of refraction is 90 degrees.
(B) The angle of incidence at which the light is completely reflected.
(C) The angle of incidence at which the light is not refracted at all.
(D) None of the above.Total internal reflection can be used to create optical fibers. Optical fibers are thin strands of glass or plastic that are used to transmit light. How does total internal reflection work in optical fibers?
(A) Light is reflected off of the walls of the fiber, which keeps it from escaping.
(B) Light is refracted as it passes through the fiber, which keeps it from escaping.
(C) Light is absorbed by the fiber, which keeps it from escaping.
(D) None of the above.A mirage is an optical illusion that can be seen in hot, dry weather. It is caused by the refraction of light as it passes through layers of air with different temperatures. What type of mirage is seen when the sky appears to be a pool of water?
(A) A superior mirage
(B) An inferior mirage
(C) A Fata Morgana
(D) None of the above.A Fata Morgana is a type of mirage that is often seen in the Arctic and Antarctic. It is caused by the refraction of light as it passes through layers of air with different temperatures and densities. What does a Fata Morgana typically look like?
(A) A city or other object that appears to be floating in the air.
(B) A rainbow that appears to be upside down.
(C) A reflection of the sky on the ground.
(D) None of the above.The twinkling of stars is caused by the refraction of light as it passes through the Earth’s atmosphere. What causes the light to be refracted?
(A) The different temperatures of the air in the atmosphere.
(B) The different densities of the air in the atmosphere.
(C) The different pressures of the air in the atmosphere.
(D) None of the above.