1. The problem statement, all variables and given/known data The interference pattern in this image: http://session.masteringphysics.com/problemAsset/1074248/3/22.P45.jpg is seen on a screen 1.0m behind an 950 lines/mm diffraction grating. What is the wavelength of the light? (expressed in nanometers to 2 sig figs) 2. Relevant equations I know that the equation relating the variables is: d sin(theta)=m(lambda) where theta is the angle from the center maximum to the mth maxima. d being the distance between slits in the grating. And using the small angle approximation I think you can replace sin(theta) with y/L where y is the distance between the central maximum and the mth one and L is the distance of the screen from the grating 3. The attempt at a solution I tried plugging the variables into the equation but I can't seem to get the right answer. ie: d(y/L)=m(lambda) (1/950000)(.436/1)=1lambda lambda=460nm which is wrong What am I doing wrong?