Question

**I'm not looking for the answer, I'm looking for someone to help me solve it so i can find the answer. :)

A laser shined through a diffraction grating with lines that are 1/500 mm apart
creates a spectra on a screen. The distance from the center bar to the first side
bar is 66 mm. The distance from the diffraction grating to the first side bar is 187
mm. Calculate the wavelength of light (in nano meters) that is being emitted by
the laser.

Answer 1

for this question you only have to apply this equation:

\[n \lambda=d(\frac{ X }{ L })\]

λ = wavelength in nanometers (nm)
d = distance between the lines on the diffraction grating
n = order of the image (most often n = 1, this being the first bar/spot to one side of the center spot on the screen)
X = distance between the center spot and the first side spot
L = distance from the diffraction grating to the first side spot

What class is this from? and why don't they show you how to do this?