Which of these processes of the water cycle is a direct effect of the sun's energy?
a. evaporation
b. seeping of water into soil
c. formation of precipitation
d. runoff of water over soil

Option a) Evaporation

Explanation:

Option b) seeping of water into soil is the process by which water on the surface of earth enters soil inside earth slowly

c) formation of precipitation are developed in clouds, and clouds are formed when water vapor in the atmosphere cools and condenses. Hence cannot be direct effect of Sun energy

d) runoff of water from soil is the flow water when excess water due to flood is there, which causes soil erosion.

But our question of a direct effect of the Sun's energy is option a) evaporation.

By evaporation, we see that floor with water dry, clothes washed when put to dry dries, etc.

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.