Browse Questions

An interference pattern is obtained by using red light. If in the same set up red light is replaced by blue light the fringe width will

(a)increases

(b)decreases

(c)remain same

(d)will become faint

The fringe width $\beta= \large\frac{\lambda D}{d}$
$\therefore \beta \;\alpha\; \lambda$
as $\lambda _{Blue} < \lambda _{red}$
the fringe width will decreases.
Hence B is the correct answer.