# How Thick Is The Foil

1. Apr 30, 2013

### AyooNisto

1. The problem statement, all variables and given/known data
A fine metal foil separates one end of two pieces of optically flat glass, as in Figure 24-33 in the textbook. When light of wavelength 700nm is incident normally, 24 dark lines are observed (with one at each end).

How thick is the foil?

2. Relevant equations
t = mλ, m = 0,1,2,...

3. The attempt at a solution
because m = 0 corresponds to the edge where the glasses touch m+1 represents the number of the fringe so the thickness of the foil is

d = (1/2)(23)(700nm)
d = 8.05 * 10 ^ -6 this is not the right answer and i dont understand why where am i going wrong

Last edited: Apr 30, 2013
2. Apr 30, 2013

### barryj

3. Apr 30, 2013

### AyooNisto

the answer i keep getting is 8.05 * 10^-6 which i guesss would be a micrometer ( i edited that above) which i guess would be but the answer has to be in meters.

4. Apr 30, 2013

### barryj

I think you are correct.

5. Apr 30, 2013

### AyooNisto

wow yeah, the problem was i wasnt putting in the *10^-6.... thanks for your help stupid mistake on my part.