# Diffraction Grating Maximum Order

1. May 24, 2010

### silence98

1. The problem statement, all variables and given/known data

A grating having 1000 lines per mm is illuminated with sodium light of mean wavelength 589.3 nm. Determine the maximum order of diffraction that can be observed.

2. Relevant equations

dsin($$\theta$$)=m$$\lambda$$

d=slit spacing

3. The attempt at a solution

The order of diffraction is given by m, and m=(dsin$$\theta$$)/$$\lambda$$, so i figure m takes a maximum value when sin($$\theta$$)=1, or when m=d/$$\lambda$$ but i am not sure if this is correct.
I'd be grateful for any hints.

Last edited: May 24, 2010
2. May 24, 2010

### Stonebridge

Yes, the angle can't be greater than 90 degrees.
So if you put sin = 1 you will get a value for m that could be, for example, 3.4
This means you could get a 3rd order but not a 4th

3. May 24, 2010

thanks