Please answer question 19

Please answer question 19 Physics — Human Eve and the colorful World X C8SE up can to study scattering of tight? how

Dear student,
This activity shows the Colour of the Sun at Sunrise and Sunset due to tyndall effect.

• Place a strong source (S) of white light at the focus of a converging lens (L1). This lens provides a parallel beam of light.
• Allow the light beam to pass through a transparent glass tank (T) containing clear water.
• Allow the beam of light to pass through a circular hole (c) made in a cardboard. Obtain a sharp image of the circular hole on a screen (MN) using a second converging lens (L₂), 
• Dissolve about 200 g of sodium thiosulphate (hypo) in about 2 L of clean water taken in the tank. Add about 1 to 2 mL of concentrated sulphuric acid to the water. 

You will find fine microscopic sulphur particles precipitating in about 2 to 3 minutes. As the sulphur particles begin to form, you can observe the blue light from the three sides of the glass tank. This is due to scattering of short wavelengths by minute colloidal sulphur particles. Observe the colour of the transmitted light from the fourth side of the glass tank facing the circular hole. It is interesting to observe at first the orange red colour and then bright crimson red colour on the screen.
This activity demonstrates the scattering of light that helps you to understand the bluish colour of the sky and the reddish appearance of the Sun at the sunrise or the sunset.

Regards