Question

In double slit experiment using light of $\lambda =500$ nm, the angular width of fringe formed on distant screen is ${0.1}^o.$ What is the spacing between slits?

• A. 2.9 mm
• B. $2.9\times {10}^{-4}$ m
• C. $2.9\times {10}^{-6}$ m
• D. $2.9\times {10}^{-5}$ m

Answer 1

The correct option is B $2.9\times {10}^{-4}$ m

$\theta =\frac{\beta }{D}=\frac{D\lambda }{dD}=\frac{\lambda }{d}$
$d=\frac{\lambda }{\theta }=\frac{500\times {10}^{-9}}{0.1\times \frac{\pi }{180}}$
$=\frac{5\times {10}^{-6}}{\pi }\times 180$
$=2.86\times {10}^{-4}$ m