Question

Blue color of sky is due to:
A). Dispersion of light
B). Scattering of light
C). Reflection of light
D). Refraction of light

Answer 1

Hint: This question is based on ray optics. Define the dependence of color on the frequency and wavelength of light. The frequency of light is responsible for the color of blue sky. The light with high frequency will scatter more and with low frequency will scatter less.

Complete step by step answer:
The spectrum has lots of rays that are infrared ray, ultraviolet ray, x-ray, visible ray, micro ray, radio ray, gamma-ray.
If we arrange those rays in order of wavelength then the order will be
gamma-ray < x-ray < ultraviolet ray < visible ray < infrared ray < micro ray < radio ray
And the frequency order will be the opposite of this order.
gamma-ray > x-ray > ultraviolet ray > visible ray > infrared ray > micro ray > radio ray
In those rays only visible rays we can see because visible rays have color.
Visible rays have seven colors that are present in it which are red, violet, green, orange, indigo, blue, yellow.
The wavelength order of those 7 colors are
violet < indigo < blue < green < yellow < orange < red
and frequency order of those colors would be
violet > indigo > blue > green > yellow > orange > red
In the sky, the colors which have high frequency will scatter more because violet, indigo, and blue have a high frequency so that colors scatter more in the sky and all those colors look like blue that's why the sky looks blue.
The answer is (B).

Note: For those types of questions, students have to remember the example of all the four phenomena given in the options. Because the students will confuse between scattering and dispersion also between refraction and reflection.
Also, at the time of sunset and at the time of sunrise we see the sky red because due to the shorter wavelength or high frequency most of the blue light is scattered. Since, the red light has low frequency and longer wavelength it will not scatter more. So, we only see the red light coming from the sun since at that time the distance between the sun and us is more and the light has to cover more distance and hence, the blue light will scatter more and finally only the red light remains which is observed by us.