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 splitting of white light into its seven constituent colors (Violet, Indigo, Blue, Green, Yellow, Orange, Red - VIBGYOR) upon passing through a transparent medium such as a glass prism.

Step 2: State the cause of dispersion:
- The primary cause is the varying speeds of different colors of light within the prism medium.
- Each color, possessing a distinct wavelength, refracts (bends) by a different degree upon entering and exiting the prism.
- Violet light exhibits the maximum bending, while Red light bends the least.

Step 3: Describe the diagram:
- Depict a triangular glass prism on a surface.
- Illustrate a narrow beam of white light entering the prism, showing its subsequent split into seven colors.
- On the opposite face of the prism, show the emergent rays diverging as a fan, representing the VIBGYOR spectrum.
- Clearly label the incident ray, refracted rays, emergent rays, and the colors in their correct spectral order.

Step 4: Conclusion:
The dispersion of white light by a prism creates a visible spectrum as each light wavelength refracts differently.