Question

Plane microwaves are incident on a long slit having a width of 5 cm. The wavelength of the microwaves if the first minimum is formed at ${30}^0$ is

• A. 5 cm
• B. 5 mm
• C. 25 cm
• D. 2.5 cm

Answer 1

The correct option is D 2.5 cm

$n\lambda =\left(a\sin \theta \right)$
$a\sin \theta =n\lambda$
$a\left(\frac{1}{2}\right)=\lambda$
$\left(\frac{5}{2}\right)=\lambda$
$2.5cm=\lambda$