Question:

Total internal reflection takes place

Updated On: Aug 15, 2022
  • when a ray moves from denser to rarer and incident angle is greater than critical angle
  • when a ray moves from rarer to denser and incident angle is less than critical angle
  • when a ray moves from rarer to denser and incident angle is equal to critical angle
  • none of the above
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The Correct Option is A

Solution and Explanation

Total internal reflection is the phenomenon of reflection of light into a denser medium from an interface of denser medium and rarer medium. The essential conditions for total internal reflection are (i) Light should travel from a denser medium to a rarer medium. (ii) Angle of incidence in denser medium should be greater than the critical angle for the pair of media in contact. We may define critical angle for a pair of media in contact as the angle of incidence in the denser medium corresponding to which angle of refraction in the rarer medium is $ 90^{\circ}. $ It is represented by $C$ and its .value depends on the nature of media in contact. In total internal reflection, $100\%$ of incident light is reflected back into the same medium, and there is no loss of intensity. That is why images formed by total internal reflection are much brighter than those formed by mirrors or lenses.
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Concepts Used:

Ray Optics and Optical Instruments

Optics, deals with the determination of behaviour and the properties of light, along with its interactions with the matter and also with the instruments that are used to detect it.

Ray optics is also known as the geometrical optics and it is a branch of science which describes light propagation.

Reflection is the change in direction of light at an interface in-between two different media so that the wave-front returns into a medium from which it was originated.

Speed of light is the rate at which the light travels in free space.

A phenomenal change in image formed when the light is passed from one medium to another which is called Refraction.

Total Internal Reflection is the reflection of light when the light ray enters into a rarer medium from a denser medium and the angle of incidence is higher than the critical angle of incidence then that light ray will be reflected back to the denser medium.

Read More: Ray Optics and Optical Instruments