Question

For bright fringes, the path difference due to reflected light is must be equal to

• A. $2n\pi$
• B. $(2n+1)\frac{\pi }{2}$
• C. $n\lambda$
• D. $(2n+1)\frac{\lambda }{2}$

Answer 1

The correct option is D $(2n+1)\frac{\lambda }{2}$

the total path difference must be of the form $n\lambda$
but as the suffers reflection it already suffers a path difference of $\frac{n\lambda }{2}$
so for a reflected wave path difference is $(2n+1)\frac{\lambda }{2}$
option $D$ is correct