Question

Light of wavelength $5000Å$ is incident over a slit of width $1\mu m$ . The angular width of central maxima will be

• A. $30^{\circ }$
• B. $60^{\circ }$
• C. $90^{\circ }$
• D. $120^{\circ }$

Answer 1

Answer: (B)

For first minima
$sin\theta =\frac{\lambda }{a}=\frac{5000\times 10^{-10}}{1\times 10^{-6}}=\frac{1}{2}$
$\Rightarrow$ $\theta =30^{\circ }$
So the angular width of the central maxima is
$2\theta =60^{\circ }$