MP8-2: Single slit diffraction (spoiler)

I found it helpful to convert to micrometers for each individual measurement. Note the "0.5" in the denominator. I need this because the distance to the central point is only half the distance given of 17.9mm. The "3" in the numerator represents m=3 for the third minimum.

For Part B, recall the equation for refraction m1*lambda1=m2*lambda2. Since water has a higher index of refraction than air, the wavelength will become shorter in water as compared with the original. Since the width of the fringes is proportional to lambda, this will make them narrower.