Question

What is the path difference between two waves $1$ and $2$ shown below?

• A. $t(\mu -1)$
• B. $t(\frac{1}{\mu }-1)$
• C. $t(1-\frac{1}{\mu })$
• D. $t(\mu +1)$

Answer 1

The correct option is A $t(\mu -1)$


Path length of wave $1$ in air film $=t$

Path length of wave $2$ in liquid $=t$

So, path length of wave $2$ in air film $=\mu t$

Therefore, path difference,

$\Delta x=\mu t-t=t(\mu -1)$

Hence, $\left(A\right)$ is the correct answer.