Question

A parallel beam of light of wavelength $\lambda$ is incident normally on a narrow slit. A diffraction pattern is formed on a screen placed perpendicular to the direction of the incident beam. At the second minimum of the diffraction pattern, the phase difference between the rays coming from the two edges of slit is

• A. $\pi \lambda$
• B. $2\pi$
• C. $3\pi$
• D. $4\pi$

Answer 1

The correct option is D

$4\pi$

Path difference $\Delta x=n\lambda ,$ Phase difference $\left(\Delta \varphi \right)=2n\pi$

$\therefore n=2,\Delta \varphi =2\times 2\times \pi =4\pi$