Question

A double slit experiment is conducted in air using a laser at 532nm and a slit separation of 20um. What happens to the fringe spacing if the entire experiment is now immersed in water?

A. The fringe spacing will remain the same
B. The fringe spacing will increase
C. The fringe spacing will decrease

Answer 1

Option B - The fringe spacing will increase

Step-by-step explanation:

We are given;

Wavelength; λ = 532nm

slit separation; d = 20um

For double-slit experiment, the fringe width is given by the expression;

β = λD/d

Where;

β is the fringe width

λ is the wavelength

D is the distance between the screen and the slit

d is the slit separation

Now, when immersed in water, the slit separation distance will decrease.

Now, from the fringe width equation, when "d" decreases, it means that we will have a bigger value of fringe width.

Thus, as slit separation decreases, the fringe width increases.