1. Light of wavelength 632.8nm is normally incident upon a grating of 5000 lines/cm. How many different diffraction orders can be seen in transmission? 2. m(lambda)=d(sintheta) 3. According to my text, d=1/5000lines/cm = 2x10^-6m and sintheta= lambda/d = 632.8x10^-9/ 2x10^6 = .3164 If I take sin^-1(.3164), I get 18 degrees. From here, I don't know what to do because the answer is that 7 beams exist, corresponding to 4 orders, and I don't know how to get to that answer!