# Homework Help: How many bright fringes?

1. Feb 8, 2017

### Starrrrr

1. The problem statement, all variables and given/known data
At most, how many bright fringes can be formed on either side of the central bright fringe when light of wavelength 644 nm falls on a double slit whose slit separation is 3.64 × 10-6 m?

2. Relevant equations
m=dsintheta/lamdba

3. The attempt at a solution
m=(3.64x10e-6)(1)/644x10e-9) = 5.65 which is 6 bright fringes right but the system telling me it's wrong?

2. Feb 8, 2017

### blue_leaf77

What is the width of each slit? Without this information your question cannot be answered.

3. Feb 8, 2017

### Starrrrr

That's the full question.

4. Feb 8, 2017

### ehild

Can the 6th fringe form?

5. Feb 9, 2017

### Starrrrr

I'm not sure so I'm guessing no

6. Feb 9, 2017

### haruspex

Last time I checked, 5.65<6.

7. Feb 9, 2017

### ehild

What would be sin(θ) at the 6th fringe? Is it possible?

8. Mar 30, 2018

### Barbie Voss

The brightness fringe should not be rounded from the equation. so yes the answer from the equation is 5.65. Which makes the greatest fringe 5 not 6.