What is the correct thickness of the foil based on the observed dark lines?

[AyooNisto]

Homework Statement

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?

Homework Equations

t = mλ, m = 0,1,2,...

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 don't understand why where am i going wrong

 

[barryj]

what are the units of your answer?

 

[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.

what are the units of your answer?

 

[barryj]

I think you are correct.

 

[AyooNisto]

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

I think you are correct.