Question

If in a Young's double slit experiment, the slit width is 3 cm, the separation between slits and screen is 70cm and wavelength of light is 1000 A , then fringe width will be ($\mu$ = 1.5)

• A. $2.3\times {10}^{-3}cm$
• B. $2.3\times {10}^{-4}m$
• C. $2.3\times {10}^{-5}cm$
• D. $2.3\times {10}^{-6}m$

Answer 1

The correct option is B $2.3\times {10}^{-4}m$

We have fringe width,
$\beta =\frac{\lambda D}{d}$
We have $\lambda =1000A^o={10}^{-5}cm$, $d=3cm$, $D=70cm$
$⟹\beta =\frac{{10}^{-5}\times 70}{3}=2.3\times {10}^{-4}cm$