Coherent, monochromatic light is incident on a pair of slits that are 0.3 mm apart. When light passes through the slits and strikes a screen 1.5 m away, the distance between the 3rd and 5th order maximum is 5.5 mm. What is the wavelength of the light being used?

550 nm

Explanation:

The formula for the double-slit diffraction experiment is:

where

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

is the wavelength of the light used

D is the distance of the screen from the slits

d is the separation between the slits

In this problem we have:

is the distance between the slits

is the distance of the screen

We also know that the distance between the 3rd and 5th order maximum is 5.5 mm, which means that:

And we can rewrite this as:

where we used respectively m=3 and m=5. If we know solve for , we find the wavelength:

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