Consider red light with a wavelength of 692 nm in air that is incident onto two slits such that it gives diffraction fringes that are 1.00 mm apart on a screen at a distance l from the slits. if the screen is moved back by an additional 4.00 cm, the fringes become 1.20 mm apart. what is the separation between the slits?

The separation between slits is:

Explanation:

The distance between adjacent maxima is given by the following expression:

For the distance between maxima being 1mm (let's solve all this problem using milimeters) we have the following:

(1)

For the second condition in which the screen is moved 40 mm away we have the following:

(2)

Using equation 1 we can write:

Plugging the value of L in equation 2 brings us to

We could also as a bonus find L which is just

I'll leave that up to you! Good luck!

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