Question

why do we get the seven colours from white light? plss answer

Answer 1

Well the white light is a mixture of a large number of wavelengths of lights. These different wavelengths of lights travell at different speed in the medium such as glass. In air and vacuum the have alsmost the same speed. But in prism the travell with t\different speeds. So when the pass prism the length of path travelled in the same times is different and hence when the emerge out, the different colrs are at differemt positions resulting in a seperation of colours.
This is called the dispersion of light.

Answer 2

Heya☺
When a beam of a white light is passed through a glass prism, is called spectrum.
There are seven colours comes i n prism violet, indigo, red, green, yellow, orange, red can be memoriesd by VIBGYOR. Splitting up white light into seven colours is called dispersion of light.