# Homework Help: Amplitude of multislit grating

1. Jan 31, 2006

### UrbanXrisis

The formula for the amplitude for a multislit grating is:

$$A(Y,t)=\frac{M}{R}cos \left(\frac{2 \pi R}{\lambda}-2 \pi f t \right) \frac{sin^2 \left[(2N+1) \frac{x}{2}\right]}{sin^2 \left[\frac{x}{2}\right]}$$

a spectra would look something like this

I am trying to find a formula not for the amplitude of the giant maximas but of the height of the maxima right after the giant maxima.

so I know maxima's occur when the denominator of sine is much smaller than the numerator. But how would I equate the maxima height right after the giant maxima?