Activity of Integration 5 (page 54) Imagine one of the daily newspapers in your country has published an article entitled "The sun will soon stop moving". The National Science Forum has organized a conference to discuss the newspaper article, and your school has been invited to participate in the discussion. Using the knowledge, you have learnt in this chapter, prepare a paper of at least one and a half pages that you will present at the conference. In your paper, point out the likely effects on time and people's lives if the sun stopped moving.

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.