# Refractive Index of the Material of Prism – Viva Voice | Physics Class 11

## Viva Voice Questions with Answer Refractive Index of the Material of Prism For: Science Class 11 | Physics

Q.1: What is a prism?
Ans. A piece of transparent medium bounded by three rectangular and two triangular surfaces.

Q.2: Define deviation.
Ans. Total bending of a ray of light while crossing on optical medium.

Q.3: Define angle of deviation (D).
Ans. The angle between the incident ray and the emergent ray.

Q.4: What is the relation between the angle of incidence and the angle of deviation?
Ans. When the angle of incidence starts increasing from a smaller value, at first the angle of deviation decreases up to a certain limit (angle of minimum deviation) and then it increases.

Q.5: How does the angle of deviation vary with the wave length?
Ans. Shorter the wavelength, greater will be the angle of deviation.

Q.6: What is the relation between wavelength and energy?
Ans. Inverse proportion i.e. shorter the wavelength, greater is the energy of a colour.

Q.7: What is angle of prism in this experiment?
Ans. 60o.

Q.8: How angle of prism is related with the angle of deviation?
Ans. larger the angle of prism, larger is the angle of deviation.

Q.9: Give some examples of total internal reflection.
Ans. (a) Mirage (b) Glittering of precious stones (c) Shiny appearance of the water surface of swimming pools as seen from inside the water.

Q.10: When light enters into the prism is there any change in the frequency of wave length?
Ans. The wavelength decreases but the frequency does not change.

Q.11: What is the relation between the speed of light (C) frequency (υ) and wave length (λ)?
Ans. C = υ x λ

Q.12: What is unit of refractive index?
Ans. No units, because it is the ratio between two similar quantities.

Q.13: Which of the colours have maximum and minimum angle of deviations?
Ans. The deviation is greater in the violet colour and smallest is red.

Q.14: Why the danger signals are red?
Ans. Since the deviation in the red colour is minimum, therefore, they can be seen from the maximum distance.

Q.15: Define dispersion of light.
Ans. Separation of colours present in polychromatic light by a prism.

Q.16: Give any example of dispersion.
Ans. Rainbow in the sky due to droplets of water.

Q.17: What are totally reflecting prisms?
Ans. The prisms in which the angle of prism are 90o, 45o and 45o.

Q.18: What kind of glass is used for making prism?
Ans. Crown glass or optical glass.

Q.19: Why is PO cut equal to OM in this experiment?
Ans. Because the image is formed at the same distance behind as the object is in front of the reflecting face of the prism.

Q.20: What is meant by critical angle?
Ans. When refraction takes place from a denser to a rare medium, that angle of incidence for which the angle of refraction is 90o, is called the critical angle.

Q.21: What is totally reflecting prism?
Ans. It is a glass prism having angles of 45o, 45o, 90o. It deviates the path of light through 90o or180o without any loss in intensity.

Q.22: Why do the precious stones like diamond glitter?
Ans. These precious stones have large refractive indices and small critical angles which make the incoming light totally reflected a number of times without much loss in intensity and hence make their faces look bright.

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