Question

The path difference produced by two waves is 3.75 $\mu$m and the wavelength is 5000 $\mathring {A}$. The point is

• A. uncertain
• B. dark
• C. partially bright
• D. bright

Answer 1

Answer: (B)

dark

Answer 2

Given, path difference $? x = 3.75 \, \mu m = 3.75 \times 10^{-6} \, m$ and
Wavelength $\lambda = 5000 \mathring {A} = 5 \times 10^{-7} \, m$
$\frac{? x}{\lambda} = \frac{3.75 \times 10^{-6}}{5 \times 10^{-7}}$
$= \frac{37.5}{5} = 7.5$
$\therefore ? x = 7.5 \lambda$
Here, $? x$ is odd multiple of $\lambda$, so point is dark.