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sghaussi

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**slit diffraction in water?**

Hello! I'm having trouble answer this homework problem:

**Suppose the entire apparatus (light of wavelength X nm from a distant source is incident on a slit Y mm wide, and the resulting diffraction pattern is observed on a screen Z m away) is immersed in water (n=1.33).**

Then what is the distance between the two dark fringes on either side of the central bright fringe?

Then what is the distance between the two dark fringes on either side of the central bright fringe?

I know what I want to use the equation for Dark fringes in single-slit diffraction:

sin(theta) = m*lamda/a

in my case, m = 1

and a = y

I'm not sure how to solve this problem now that the entire apparatus is immersed in water? I know water affects this, but how? Can you help me start this problem?