Question

A double slit interference experiment is carried out in air and the entire arrangement is dipped in water. The fringe width

• A. increases
• B. decreases
• C. remains unchanged
• D. fringe pattern disappears

Answer 1

The correct option is B

decreases

Explanation for the correct option:

In case of option B:

1. When the entire arrangement is dipped in water, the wavelength of light decreases.
2. Fringe width is directly proportional to the wavelength of light used.
3. Therefore, fringe width decreases.

Explanation for the incorrect options:

In case of option A:

1. In water wavelength of the light decreases hence fringe width decreases.

In case of option C:

1. Distance between slits and screen and slit width is unchanged but wavelength decreases.
2. Thus fringe width will change.

In case of option D:

1. Here, the entire arrangement is dipped into the water so, there will be interference.
2. Thus, an interference pattern will be observed.

Hence, option B is the correct answer.