Explanation:

Dispersion of white light is the separation of white light into its constituent colors. This can be achieved by passing white light through a prism. The different colors of the spectrum refract by different amounts when passing through the prism, resulting in the separation of the colors.

Identification of Colors:

In the given diagram, we can see that white light is entering the prism from one side and getting dispersed into its constituent colors. At the other end of the prism, we can see that these colors are converging again to form white light.

The colors marked as P and Q respectively are:

- P: Violet
- Q: Red

Therefore, the correct answer is (a) Red and Violet.

Explanation of Colors:

When white light enters the prism, it undergoes refraction and gets dispersed into its constituent colors. The amount of refraction depends on the wavelength of the light. Violet light has the shortest wavelength and hence undergoes the maximum refraction. Red light has the longest wavelength and undergoes the least refraction.

Therefore, the colors are arranged in the following order from maximum to minimum refraction:

Violet, Indigo, Blue, Green, Yellow, Orange, Red

This arrangement is commonly known as ROYGBIV, where each letter represents the first letter of each color.

Conclusion:

In conclusion, when white light is passed through a prism, it gets dispersed into its constituent colors due to refraction. The colors are arranged in the order of ROYGBIV, with the maximum refraction occurring for violet light and the least for red light. In the given diagram, the colors marked as P and Q respectively are red and violet.

Red and violet