Why we sees different colour in rainbow?

Why we sees different colour in rainbow?

 PROF WAQAR HUSSAIN  

       

     When sun rays fall on a drop of water hanging in the sky, they are split up into seven constituent colours; Violet, Indigo, Blue, Green, Yellow, Orange and Red. A rainbow is thus formed by combined refraction, dispersion and internal reflection of sun’s rays on rain drops.

     The light is first refracted as it enters the surface of the raindrop, then reflected off the back of the drop, and again refracted as it leaves the drop.

The incoming light is reflected back over a wide range of angles, with the most intense light at an angle of 40°–42°. The angle doesn’t depend on the size of the drop, but on its refractive index.

The rain drops act like so many glass prisms splitting up the sunlight which enters them. When infinite number of rays strike a number of droplets they form arc of a circle and are called the rainbow. Rainbow is seen when the sun is at the back of the observer and sun rays fall on the tiny drops in front.