1. Fill in the blanks and explain the completed sentences.
(a) Refractive index depends on the …………. of light.
(b) The change in ……………. of light rays while going from one medium to another is called refraction.
(a) Refractive index depends on the velocity of light.
(b) The change in the direction of propagation of light rays while going from one medium to another is called refraction.
(a) If the angle of incidence and angle of emergence of a light ray falling on a glass slab are i and e respectively, prove that, i = e.
(b) A rainbow is the combined effect of the refraction, dispersion, and total internal reflection of light.
Rainbow is a beautiful natural phenomenon. It is the combined effect of dispersion, refraction and total internal reflection of light. It can be seen mainly after a rainfall. Small droplets of water act as small prisms. When light rays from the Sun enter these droplets, it gets refracted and dispersed. Then there is internal reflection as shown in the figure, and after that once again the light gets refracted while coming out of the droplet. All these three processes together produce the rainbow.
3. Mark the correct answer in the following questions.
A. What is the reason for the twinkling of stars?
(i) Explosions occurring in stars from time to time
(ii) Absorption of light in the earth’s atmosphere
(iii) Motion of stars
(iv) Changing refractive index of the atmospheric gases
B. We can see the Sun even when it is little below the horizon because of
(i) Reflection of light
(ii) Refraction of light
(iii) Dispersion of light
(iv) Absorption of light
C. If the refractive index of glass with respect to air is 3/2, what is the refractive index of air with respect to glass?
(i) 1/2
(ii) 3
(iii) 1/3
(iv) 2/3
A. What is the reason for the twinkling of stars?
(i) Explosions occurring in stars from time to time
(ii) Absorption of light in the earth’s atmosphere
(iii) Motion of stars
(iv) Changing refractive index of the atmospheric gases
B. We can see the Sun even when it is little below the horizon because of
(i) Reflection of light
(ii) Refraction of light
(iii) Dispersion of light
(iv) Absorption of light
C. If the refractive index of glass with respect to air is 3/2, what is the refractive index of air with respect to glass?
(i) 1/2
(ii) 3
(iii) 1/3
(iv) 2/3
(a) If the speed of light in a medium is 1.5 x 108 m/s, what is the absolute refractive index of the medium? Ans : 2
Ans. (for directly to the above sums slide over the duration to 0:37:36)
(b) If the absolute refractive indices of glass and water are 3/2 and 4/3 respectively, what is the refractive index of glass with respect to water? Ans : 9/8
Ans. (for directly to the above sums slide over the duration to 0:56:36)