Question

The ratio of speed of light in a vacuum to the speed of light in a particular material is called what?
A) The coefficient of diffraction of the material.
B) The index of refraction of material.
C) The coefficient of refraction to the material.
D) The index of diffraction of the material.

Answer 1

Three phenomena of light are which are widely studied.

1. Dispersion of sunlight by raindrops in the atmosphere.
2. Refraction of white light by different amounts due to which an arch of rainbow is formed.
3. Total internal reflection within the raindrop. In refraction the light travels from one medium and enters to another, and hence gives our answer.

Step by step solution:
Step 1:
There are some phenomena of light which are read in our classes. Now we will get a brief explanation of these phenomena and infer our solution.
Refraction: When electromagnetic radiation, in the form of visible light, travels from one substance or medium into another, the light waves may undergo a phenomenon known as refraction, which is manifested by a bending or change in direction of the light.
Dispersion: Dispersion is defined as the breaking up or scattering of something. An example of dispersion is throwing little pieces of paper all over a floor. An example of dispersion is the colored rays of light coming from a prism which has been hung in a sunny window.
Total internal reflection: When light rays strike the inside surface of a right-angled glass prism with an angle of incidence, which is greater than the critical angle then total internal reflection occurs.
Step 2:
From the above definition we can say that when light travels from one medium to another, say from vacuum to a particular medium, refraction occurs. Definition of refractive index will make crystal clear about the solution.
Refractive index: The ratio between the speed of light in medium to speed in a vacuum is the refractive index. When light travels in a medium other than the vacuum, the atoms of that medium continually absorb and re-emit the particles of light, slowing down the speed of light.
Refractive index of material =$\dfrac{{{V_{vacuum}}}}{{{V_{material}}}}$ .

Hence, option B is correct.

Note: Two types of refractive index Relative refractive index– It is the ratio of speed of light in one medium to the speed of light in another medium. The absolute refractive index is defined as the ratio of the speed of light in vacuum and in the given medium. The absolute refractive index should never be less than 1.