# Diffraction grating and red light

1. Nov 17, 2008

### Kris1120

1. The problem statement, all variables and given/known data
White light is spread out into its spectral
components by a diffraction grating.
If the grating has 2469 lines/cm, at what
angle does red light of wavelength 635 nm
appear in first order?

2. Relevant equations

sin(theta) = m($$\lambda$$ /d)

3. The attempt at a solution

theta = inverse sin [( 1 * 635 e-9 m) / 24.69 m} = 1.4735 e -6 degrees

2. Nov 17, 2008

### alphysicist

Hi Kris1120,

In your formula, d is the distance between grating lines. If there are 2469 lines in every cm, what is the distance between each line?

3. Nov 17, 2008

### Kris1120

I see... its 1 / 2469 cm! Thank you!

4. Nov 17, 2008

### alphysicist

That's right (as long as you meant (1/2469) cm; some people inadverdently put the cm in the denominator for this type of problem).