Question

What is dispersion of white light ? State its cause. Draw a diagram to show dispersion of a beam of white light by a glass prism.

Answer 1

Step 1: Define dispersion of white light:
Dispersion of white light is the phenomenon in which white light splits into its seven constituent colors when it passes through a transparent medium like a glass prism.
These colors are: Violet, Indigo, Blue, Green, Yellow, Orange, and Red (VIBGYOR).

Step 2: State the cause of dispersion:
- The main cause of dispersion is that different colors of light travel at different speeds in the prism medium.
- Each color has a different wavelength, and hence, each color bends (refracts) by a different amount when it enters or exits the prism.
- Violet light bends the most, and Red light bends the least.

Step 3: Describe the diagram:
- Draw a triangular glass prism placed on a table.
- Show a narrow beam of white light - Inside the prism, indicate that the light splits into seven colors.
- From the other face of the prism, draw the emergent rays spreading outwards in a fan shape to represent the colors of the spectrum (VIBGYOR).
- Label the incident ray, refracted rays, emergent rays, and the colors in correct order.

Step 4: Conclusion:
Dispersion of white light through a prism results in the formation of a visible spectrum due to different degrees of refraction for each wavelength of light.