Question

Direction of the first secondary maximum in the Fraunhoffer diffraction pattern at a single slit is given by (a is the width of the slit):

• A. $a \sin \theta=\frac{\lambda}{2}$
• B. $a \cos \theta=\frac{3 \lambda}{2}$
• C. $a \sin \theta=\lambda$
• D. $a \sin \theta=\frac{3 \lambda}{2}$

Answer 1

Answer: (D)

Relation for the maximum
$\frac{(2 n+1) \lambda}{2}=a \sin \theta$
$\frac{(2 \times 1+1) \lambda}{2}=a \sin \theta[n=1]$
$\frac{3 \lambda}{2}=a \sin \theta$