Changes in a Diffraction Pattern when the Apparatus is Immersed in Water

When the whole apparatus is immersed in water, several changes can be observed in the diffraction pattern. These changes are due to the difference in the refractive index of water compared to air and can be explained using the concept of diffraction and wave optics.

1. Central Maximum:
The central maximum is the bright central region of the diffraction pattern. When the apparatus is immersed in water, the width of the central maximum decreases. This means that the central bright region becomes narrower.

Explanation:
- Diffraction occurs when a wave encounters an obstacle or aperture. In the case of a single slit or aperture, the diffraction pattern consists of a central maximum and a series of alternating bright and dark fringes on either side.
- The width of the central maximum is determined by the wavelength of the light used and the size of the aperture.
- When the apparatus is immersed in water, the wavelength of light remains the same.
- However, the refractive index of water is higher than that of air. This means that light waves will slow down when passing from air to water.
- As the light waves slow down, the effective width of the aperture decreases.
- The narrower aperture leads to a narrower central maximum in the diffraction pattern.

2. Other Fringes:
Apart from the central maximum, other fringes in the diffraction pattern may also be affected when the apparatus is immersed in water.

Explanation:
- The width of the other fringes, both bright and dark, depends on the size of the aperture and the wavelength of light.
- When the apparatus is immersed in water, the wavelength of light remains the same.
- However, the refractive index of water is higher than that of air, causing the light waves to slow down.
- The slower speed of light affects the width of the fringes, making them narrower or wider depending on the specific conditions of the experiment.

In conclusion, when the apparatus is immersed in water, the width of the central maximum in the diffraction pattern decreases. This is due to the higher refractive index of water, which causes the light waves to slow down and results in a narrower effective aperture. The other fringes in the pattern may also be affected, depending on the specific conditions of the experiment.