Question

Is Young's double-slit experiment, the slots are separated by 0.28 mm and the screen is placed 1.4 m away. If the distance between the central bright fringe and the fourth bright fringe is 1.2 cm, determine the wavelength of light used in the experiment.

Answer 1

The fringe width is given as

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

Hence the distance between central bright fringe and fourth bright fringe=$4\beta =1.2\times {10}^{-2}m$

$⟹4\times \frac{D\lambda }{d}=1.2\times {10}^{-2}$

$\lambda =\frac{1.2\times {10}^{-2}\times 0.28\times {10}^{-3}}{4\times 1.4}$

$=600nm$