Asked by Tony

A surprising result of wave theory is that the diffraction pattern of a dark screen with a hole cut in it (of arbitrary shape) is identical to the pattern of an object with the same shape as the hole.

An application of this principle is that a line mounted on transparent slide casts the same diffraction pattern as a dark film with a slot of equal size cut in it. This principle is used to measure the width of a hair. If the distance between the first spot and the central minimum is s = 1.6 cm, L = 8 m, and λ = 3 x 10^–7 m, what is the width of the hair?


So, I'm trying to apply this formula: s/L = λ/d --> and I am looking for d.
So rearranged, the formula would be d = λL/s
I convert all the units properly and then the answer I get is d = 0.15 millimeters.

Am I doing it right or am I not even using the right formula. I'm a little confused by what "s = the distance between the first spot and the central minimum" means. Please help!
Answered by bobpursley
That is the formula, almost,but for small angles, it is ok to use.
The width of a human hair is .15mm for a black person. For caucasians, it is about half that.
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