# Slits per cm on diffraction grating

1. Apr 5, 2009

### msk172

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

Light of 650 nm can be seen in three orders in a particular grating. About how many slits per cm does this grating have?

2. Relevant equations

Yikes.

3. The attempt at a solution

Either this question is ridiculously hard resulting in me not even having a clue where to start, or it is so easy that I don't even deserve to get it right.. haha. If someone could just point me towards the right CONTINENT, I might have a chance.. heh. Thanks in advance.

2. Apr 5, 2009

### Redbelly98

Staff Emeritus
3. Apr 5, 2009

### msk172

I understand that, but without knowing the length of the grating, how could one possible ascertain slits / cm?

4. Apr 5, 2009

### Redbelly98

Staff Emeritus
The equation gives you the distance between adjacent slits. Take the reciprocal of that distance (in cm), and you get the number of slits per cm.

5. Apr 5, 2009

### msk172

Got it. Ugh. Too many hours of looking at this screen. Thanks for your time.

6. Apr 5, 2009

### Redbelly98

Staff Emeritus
You're welcome, no problem.