# Homework Help: Dark fringes problem

1. Nov 27, 2004

### NotaPhysicsMan

Hey, another question I'm working on.

How many dark fringes will be produced on either side of the central maximum if light, (651nm) is incident on a single slit that is 5.47 x 10^-m wide?

Ok, I figure I could use this forumula sin@= m x lambda/Width. Am I trying to locate the maximum m (the order of the dark fringe) that it'll go?

I tried solving for m=1 and got a angle of 6.83 degrees. Now where to?
Any tips/hints welcome.

Thanks.

2. Nov 27, 2004

### Gokul43201

Staff Emeritus
What do you know about the range of values of sin@ ?

3. Nov 27, 2004

### NotaPhysicsMan

I missed something, the W is suppose to be 5.47x10^-6 m. Well, I know it can't go past 90 degrees and the min is the central max, which is 0 degrees.

4. Nov 27, 2004

### NotaPhysicsMan

So if I put sin90=m x lambda/W and solve for m, then I'll get 8.40? so 8 dark fringes?

5. Nov 27, 2004

### NotaPhysicsMan

can someone verify please and thanks