Question

In Young's double slit experiment, distance between two slits is 0.28 mm and distance between slits and screen is 1.4 m. Distance between central bright hinge and third bright fringe is 0.9 cm, what is the wavelength of light used ?

• A. $5000A^o$
• B. $6000A^o$
• C. $7000A^o$
• D. $9000A^o$

Answer 1

The correct option is B $6000A^o$

Given, $d=0.28mm=0.28\times {10}^{-3}m,D=1.4m$
$\beta =0.9cm=0.9\times {10}^{-2}m$

$\beta =3\frac{D\lambda }{d}$

or $\lambda =\frac{\beta d}{3D}$
or $\lambda =\frac{0.9\times {10}^{-2}\times 0.28\times {10}^{-3}}{3\times 1.4}$
or $\lambda =6\times {10}^{-7}m=6000A^o$