Physics Multiple Choice Questions on “Ray Optics – Total Internal Reflection”.
1. What causes haloes (rings) around the sun or the moon?
a) Total internal reflection
b) Refraction of light
c) Reflection of light
d) Dispersion
Answer: c
Clarification: When the sun or the moon is seen through a thin veil of high clouds, haloes, i.e. rings, are seen. These are formed due to the reflection of light by the icy crystals present in the atmosphere. So, this is the cause of rings around the sun or the moon.
2. Why is the sequence of colors in the secondary rainbow reverse of that in the primary rainbow?
a) Refraction of light
b) Two internal reflection
c) Reflection of light
d) Dispersion
Answer: b
Clarification: The sequence of colors in the secondary rainbow is the reverse of that in the primary rainbow because a secondary rainbow is formed by two internal reflections of light in water droplets while a primary rainbow is formed by just one total internal reflection.
3. Which of the following is a necessary condition for total internal reflection?
a) The angle of incidence in the denser medium must be greater than the critical angle for the two media
b) The angle of incidence in the rarer medium must be greater than the critical angle for the two media
c) The angle of incidence in the denser medium must be lesser than the critical angle for the two media
d) The angle of reflection in the denser medium must be greater than the critical angle for the two media
Answer: a
Clarification: The necessary conditions for total internal reflection are ➔ the light must travel from an optically denser to an optically rarer medium and the angle of incidence in the denser medium must be greater than the critical angle for the two media.
4. Which of the following color is the ocean?
a) Black
b) Orange
c) Blue
d) Red
Answer: c
Clarification: The Ocean is blue because water absorbs colors in the red part of the light spectrum. Like a filter, this leaves behind colors in the blue part of the light spectrum for us to see. So, the blue color of the ocean is due to the preferential scattering of light by water molecules.
5. The secondary rainbow is brighter than the primary rainbow.
a) True
b) False
Answer: b
Clarification: Light suffers two total internal reflections in the formation of the secondary rainbow. So more light intensity is absorbed. Therefore, the secondary rainbow will be fainter compared to the primary rainbow and the latter will be brighter.
6. ‘X’ is an optical illusion observed in deserts or over hot extended surfaces like a coal-tarred road, due to which a traveler sees a shimmering pond of water some distance ahead of him and in which the surrounding objects like trees appear inverted. Identify X.
a) Mileage
b) Mirage
c) Optical activity
d) Total internal reflection
Answer: b
Clarification: Mirage is an optical illusion observed in deserts or over hot extended surfaces like a coal-tarred road, due to which a traveler sees a shimmering pond of water some distance ahead of him and in which the surrounding objects like trees appear inverted.
7. Identify the principle behind the sparkling of diamonds.
a) Total internal reflection
b) Refraction
c) Reflection
d) Optical activity
Answer: a
Clarification: The faces of a diamond are cut suitably so that light entering it suffers total internal reflections repeatedly and gets collected inside but it comes out through only a few faces. Diamond sparkles when seen in the direction of emerging light.