Question

A laser beam is used in Young’s double slit experiment with slits separated by a distance 1.55*10-4 m. The screen is located at a distance of 2.75 m from the slits. The distance between the central bright fringe and the third order bright fringe is 0.048 m. Find the length of laser light used in the experiment.

Answer 1

Answer:

902 nm

Explanation:

We can solve the problem by using the formula for the diffraction from double slit:

$y=\frac{m\lambda D}{a}$

where:

y is the distance of the m-th order diffraction maximum from the central fringe

$\lambda$ is the wavelength of the light used

D is the distance of the screen from the slits

a is the distance between the slits

In this situation, we know:

$a=1.55\cdot 10^{-4} m\\D = 2.75 m$

And also,

y = 0.048 m for m = 3 (third order bright fringe)

Solving the equation for $\lambda$, we find the wavelength:

$\lambda = \frac{ya}{mD}=\frac{(0.048)(1.55\cdot 10^{-4})}{3(2.75)}=9.02\cdot 10^{-7} m = 902 nm$