Question

In young's double slit experiment performed using a monochromatic light of wavelength $\lambda$, when a glass plate $(\mu =1.5)$ of thickness $x\lambda$ is introduced in the path of the one of the interfering beams, the intensity at the position where the central maximum occurred previously remains unchanged. The value of $x$ will be:

• A. 3
• B. 2
• C. 1.5
• D. 0.5

Answer 1

Answer: (B)

Path difference at $O=(\mu -1)t$.
If the intensity at $O$ remains (maximum) unchanged, path difference must be $n\lambda$.
$\Rightarrow (\mu -1)t=n\lambda$
$(1.5-1)x\lambda =n\lambda$
$\Rightarrow x=2n$
For $n=1,x=2$