question_answer

What happens to the fringe pattern when the Young's double slit experiment is performed in water instead of air?

A) Shrinks                                

B) Disappear

C) Unchanged        

D) Enlarged

Correct Answer: A

Solution :

Key Idea: In water, wavelength of light decreases by a factor \[\mu ,\]the refractive index of water. In Young's double slit experiment, let screen is placed at a distance D, d is the distance  between coherent sources.                 The fringe width is given by                     \[W=\frac{D\lambda }{d}\]where, \[\lambda \] is wavelength of light used. When the whole setup is dipped in water, wavelength is \[{{\lambda }_{w}}=\frac{{{\lambda }_{a}}}{\mu },\] hence, it decreases. Therefore, fringe width decreases and hence,  fringe pattern shrinks.