Question

In the diffraction pattern due to a single slit of width '$d$' with incident light of wavelength '$\lambda$ ' , at an angle of diffraction '$\theta$' , the condition for first minimum is ____________.

• A. $\lambda \sin \theta =d$
• B. $d\cos \theta =\lambda$
• C. $d\sin \theta =\lambda$
• D. $\lambda \cos \theta =d$

Answer 1

Answer: (C)

$d\sin \theta =\lambda$

The $n^{th}$ order minima of a diffraction pattern is obtained as

$dsin\theta =n\lambda$

Hence the first minima is given as $dsin\theta =\left(1\right)\lambda$

$⟹dsin\theta =\lambda$