Question

White color of clouds is due to:
a).Reflection of seven colors of light
b).Refraction of seven colors of light
c).Scattering of seven colors of light
d).Absorption of seven colors of light

Answer 1

Hint: Use the relationship between particle size and scattering intensity to answer the question. Clouds are white because light from the Sun is white. Here, Mie scattering occurs.

Complete answer:
The reflection of the solar radiation by the earth's surface is known as albedo. It does not have any effect on the white colored appearance of clouds. Hence option a is incorrect.
Refraction of sunlight affects the sunrise or sunset but not the color of clouds. Hence, option b is not applicable.
Our atmosphere consists of many particles including dust particles, water droplets, ice crystals and other hydrometeors. Clouds also contain dust particles and water droplets. The size of the water droplets and other dust particles are larger than the wavelength of the visible light. When the solar radiation reaches the earth surface these particles scatter the incoming radiation. It has been seen that if the size of the scattering particles is larger than the wavelength of the incoming radiation then the intensity of the scattered light is of the same order for all the wavelengths of the white light. Since all the wavelengths are scattered to the same extent, when we see the scattered light, it appears to be white. This is why clouds appear white.
Absorption of light occurs when the size of the particles present is smaller to the wavelength of the light. Since the size of the particles are quite large, absorption is not possible.
Mie scattering occurs when the wavelengths of visible light are more or less equally scattered.

Thus, option c is the correct answer.

Note:
In general, it is seen that the intensity of the scattered light is inversely proportional to the fourth power of the wavelength, i.e., $I={\displaystyle \frac{1}{{\lambda }^4}}$ .
In the visible spectrum of the electro-magnetic radiation, violet light has the least wavelength and hence it is scattered the most whereas red light has the most wavelength and hence it is scattered the least.
Experimentally it has been obtained that violet light is approximately scattered $16$times more than red light.