Question

If Young's double-slit experiment is performed underwater, how would the observed interference pattern be affected?

Answer 1

The behavior of light in water:

1. Water is a denser medium for light to travel compared to air.
2. Frequency of the light remains unchanged.
3. Wavelength of the light decreases in denser mediums.
4. The formula for fringe width is $Y=\frac{\lambda D}{d}$ where $\lambda$ is the wavelength, $D$ is the distance between source and screen and $d$ is the distance between slits.
5. As the wavelength $\lambda$ is decreased, fringe width decreases.
6. Intensity of light is not affected by the change in medium.

If Young's double-slit experiment is performed underwater the fringe width of the interference pattern decreases.