# Homework Help: Measuring spacing of diffraction grating with spectroscope

1. Feb 11, 2010

### Shukie

1. The problem statement, all variables and given/known data
I have a spectroscope that looks like this:

Mercury/Helium lamp --> Split --> Lens --> Diffraction grating --> Lens --> Ocular

I want to measure the grating spacing d with this setup.

2. Relevant equations
$$d \sin{\theta} = m \lambda$$

3. The attempt at a solution
Can I simply take the first line to the left or to the right of the 'zero order line' (don't know the English translation), find the wavelength of that line in a table, measure the angle $$\theta$$ that line makes from the 'zero order line' and then calculate d? Or is it more complicated than that? Also, aside from doing multiple measurements with both lamps and taking the average, would using 'higher order lines' improve my accuracy over just using 'first order lines'?