In a double slit experiment, if the separation between the two slits is 0.050 mm and the distance from the slits to a screen is 2.5 m, find the spacing between the first-order and second-order bright fringes when coherent light of wavelength 600 nm illuminates the slits.

30 cm

Explanation:

Hi! Lets find the angles for the first and second order maxima

The first order maximum will occur for Ф=0

The second order maximum will satisfy the following relationship:

sinФ = λ/d

Where λ = 600 x 10^-9 m and d = 5 x 10^-5 m

Therefore:

sinФ = 0.012

And the vertical distance bewteen the first and second will be given by:

l = (2.5 m) tanФ

But since 2.5 m>>0.05 mm; sinФ≈tanФ

Therefore:

l = (2.5 m) sinФ

l = 0.03 m = 30 cm