Question

Explain the formation of rainbow.

(OR) 

What is the natural spectrum occurring in sky? Explain the formation of that spectrum.

Answer 1

• A rainbow is a natural spectrum of sunlight in the form of bows appearing in the sky when the sun shines on rain drops. 
• It is combined result of reflection, refraction and dispersion of sunlight from water droplets, in atmosphere. 
• It always forms in the direction opposite to the sun.
• To see a rainbow, the sun be must behind us and the water droplets falls in front of us. 
• When a sunlight enters a spherical raindrop, it is refracted and dispersed. The different colours of light are bent in different angles. 
• When different colours of light falls on the back inner surface of drop, it (Water drop) reflects (different colours of light) internally (total internal reflection). 
• The water drops again refract the different colours, when it comes out from the raindrop. 
• After leaving this different colours from the raindrop as rainbow, reach our eye. Thus, we see a rainbow.