Question

Light of wavelength $2\times 10^{-3}m$ falls on a slit of width $4\times 10^{-3}m$. The angular dispersion of the central maximum will be

• A. $30^{°}$
• B. $60^{°}$
• C. $90^{°}$
• D. $180^{°}$

Answer 1

Answer: (B)

Angular dispersion of central maximum = angular dispersion of 1st minimum $(=2\theta )$
From, $sin\theta =\frac{\lambda }{d}=\frac{2\times 10^{-3}}{4\times 10^{-3}}=\frac{1}{2}$
or $\theta =30^{°}$
$\therefore 2\theta =2\times 30^{°}=60^{°}$