Question

The path difference between two wave fronts emitted by coherent sources of wavelength $5460\mathring{A}$ is $2.1\mu \text{m}.$The phase difference between the wave fronts at that point is- (in $\text{radians}$)

• A. $7.692$
• B. $7.692\pi$
• C. $\frac{7.692}{\pi }$
• D. $\frac{7.692}{3\pi }$

Answer 1

The correct option is B $7.692\pi$

Given:
$\lambda =5460\mathring{A};\Delta x=2.1\mu \text{m}$

The relation between phase difference and path difference is,

$\Delta \varphi =\frac{2\pi }{\lambda }\Delta x$

$\Delta \varphi =\frac{2\pi }{5460\times {10}^{-10}}\times 2.1\times {10}^{-6}=7.692\pi \text{rad}$

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(B\right)$ is the correct answer.