# Question about optics (diffraction) (1 Viewer)

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#### Gza

I was working out a practice test on optics and was a little confused about how to tackle this problem:

If you illuminate a hole and project the resulting pattern on a screen- as you decrease the hole size, the screen pattern gets smaller initially and then ultimately begins to grow larger. Why is this? Derive a formula for the screen pattern diameter as a function of the hole size, distance between screen and hole and the wavelength.

I know the effect is diffraction, but deriving the mentioned relation is giving me trouble. I was thinking of using the kirchoff integral theorem, and then perhaps carrying out an integral over a rectangular aperature; but maybe that is overkill. Is their an easier way to start thinking about this?

#### Galileo

Homework Helper
Gza said:
If you illuminate a hole and project the resulting pattern on a screen- as you decrease the hole size, the screen pattern gets smaller initially and then ultimately begins to grow larger. Why is this? Derive a formula for the screen pattern diameter as a function of the hole size, distance between screen and hole and the wavelength.
Is this considered introductory physics nowadays? I must be getting old.

Maybe this will help a bit:
http://en.wikipedia.org/wiki/Diffraction

#### Gza

Lol, yeah this was probably a mispost; i got a chance to check the other posts in this section and realized it at that point. Thanks for the reference though galileo.

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