In a Young’s double-slit experiment, the slits are separated by0.28 mm and the screen is placed 1.4 m away. The distance betweenthe central bright fringe and the fourth bright fringe is measured to be 1.2 cm. Determine the wavelength of light used in theexperiment.

Given,

Distance between slits, d=0.28 mm

Distance between slits and screen, D=1.4 m

Distance between the central bright fridge and fourth bright fridge, s=1.2 cm.

Let wavelength of the light be λ

The expression for the distance is,

s=nλ D d

Substitute the values in above expression.

1.2× 10 −2 =4λ 1.4 0.28× 10 −3

λ= 1.2× 10 −2 ×0.28× 10 −3 4×1.4

λ=6× 10 −7  m

λ=600 nm

Thus, the wavelength of the light is 600 nm.