Question

A slit $4cm$ wide is irradiated with microwaves of wavelength $2cm$. What will be angular spread of central maximum, assuming incidence normal to the plane of the slit?

• A. $30^{\circ }$
• B. $40^{\circ }$
• C. $45^{\circ }$
• D. $60^{\circ }$

Answer 1

Answer: (D)

$a=4cm=4\times 10^{-2}m$
$\lambda =2cm=2\times 10^{-2}m$
Angular spread of central maximum $(2\theta )$ is
$a\sin \theta =\lambda n$
$\sin \theta =\frac{2\times 10^{-2}}{4\times 10^{-2}}$
$\Rightarrow \sin \theta =\frac{1}{2}$
$\Rightarrow \theta =30^{\circ }$
Angular spread $=2\theta =2\times 30^{\circ }$
$=60^{\circ }$