Answer the following questions in one sentence each :

1. What do you mean by optically denser or optically rarer medium ?
Ans. In refraction of light, the medium of higher refractive index is called optically denser medium, while the optically rarer medium has comparatively lower refractive index.
2. What does the refractive index depend upon ?
The refractive index depends upon the relative speed of propagation of

light in different media.
3. Name the natural phenomena seen because of atmospheric refraction. Ans. Some of the natural phenomena seen due to atmospheric refraction are :
Twinkling of stars, advanced sunrise and sunset.
4. What is dispersion of light ?
The phenomenon of spliting of light into its component colours is dispersion.

5. What is spectrum ?
The band of coloured components of a light beam is called its spectrum.

6. Whydoweseearainbowinthesky?
The beautiful phenomenon of the rainbow in the sky is because of the

combination of different phenomena like dispersion, refraction and reflection
of light.
7. A ray of light is refracted from denser medium to a rarer medium. In which direction will the ray bend ?
Ans. When a ray of light is refracted from denser medium to a rarer medium, it will bend away from the normal.
8. How will the sky appear to an astronaut in the space ? Ans. For the astronaut the sky will look black or dark.
9. Name the acronym which helps in remembering the sequence of colour formed due to dispersion of white light.
Ans. The acronym which helps us to remember the colours obtained after splitting of light is ‘VIBGYOR’.
10. Name any three phenomenon based on scattering of light.
Blue colour of sky, appearance of reddish or orange sky at sunrise or

sunset are based on scattering of light.
11. Which light is scattered easily ?
Light of shorter wavelengths is easily scattered.

12. Why red light scatters the least ?
Red light has greater wavelength than the other colours, hence it scatters

the least.
13. Which colour bends the most and the least while passing through a prism ?
Ans. Violet light bends the most and red light bends the least while passing through a prism. 

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