Question

In the diffraction of light of wavelength $\lambda$ through single slit of width d, the angle between the principal maxima and first minima will be:

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

Answer 1

The correct option is A $\lambda /d$

theory of diffraction we know that minima condition is given by

$n\lambda =d\sin \theta$

for first minima, $n=1$

$\lambda =d\sin \theta$

As $\theta \approx$ small

$\sin \theta \approx \theta$

$\lambda =d\theta$

$\theta =\frac{\lambda }{d}\to$ Required answer

$y=\frac{\lambda D}{d}$

$y=D\theta$

$\frac{\lambda D}{d}=D\theta$

$\theta =\frac{\lambda }{d}$

Required answer