$(a)$ Demonstrate an activity with a well-labelled diagram to prove that white light is made up of seven colours.
$(b)$ Which colour of light bends least and which one the most while passing out from the prism? Also,state the reason for the same.

(N/A) Take a thick sheet of cardboard and make a small hole or narrow slit in its middle. Allow sunlight to fall on the narrow slit. This gives a narrow beam of white light. Now,take a glass prism and allow the light from the slit to fall on one of its faces as shown in the figure.
Turn the prism slowly until the light that comes out of it appears on a nearby screen. We will observe that sunlight has split into seven colours. This shows that sunlight is made up of seven colours.
$(b)$ Red colour bends least while violet colour bends the most. The different colours bend at different angles with respect to the incident ray due to refraction. This happens because the speed of light of different colours is different in the glass medium,leading to different refractive indices for different wavelengths.