Name the scientist who discovered that sunlight consists of seven colours.

In the formation of spectrum of white light by a prism :

(i) which colour is deviated least?

(ii) which colour is deviated most?

What colours lie on the two sides of the 'green colour' in the spectrum of white light?

What is the order of colours in a rainbow, from the outside to the inside?

Which colour of the spectrum has

(a) longest wavelength, and

(b) shortest wavelength ?