# Diffraction?

Discussion in 'MCAT Study Question Q&A' started by m25, Sep 29, 2014.

1. ### m25

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May 28, 2014
So I heard that diffraction through an opening is most pronounced when the wave encounters an obstacle or a slit that is comparable or smaller in size to its wavelength.
But I also heard that if the slit is smaller than the wavelength, then wavelength cannot pass through the slits anymore and diffraction will be less pronounced/will not happen.

So these two contradictory statements are confusing me. Which one is right, or am I missing some sort of big picture here?

3. ### Cawolf 2+ Year Member

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Feb 26, 2013
The ideal situation is a slit of the same magnitude of the wave.

They aren't contradictory as much as they show there is an ideal range.

4. ### m25

304
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May 28, 2014
What do you mean by ideal range? And what do u mean they are not contradicting?
The first statement is saying slit size =/<wave length gives most pronounced diffraction.
The second statement is saying slit size <wave length does not give pronounced diffraction since wave is too big to pass through the slit.

5. ### Hadi7183 2+ Year Member

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Dec 8, 2013
NWT
Where did you get the second statement from? I think it's wrong. Diffraction happens when the opening size is comparable (could be smaller) to the wavelength.

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Last edited: Sep 30, 2014

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Feb 26, 2013

7. ### m25

304
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May 28, 2014
Hmm, can you elaborate on it a bit more?? I'm still confused.

8. ### Cawolf 2+ Year Member

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Feb 26, 2013
It's beyond the scope of what I can explain well on a forum given my limited knowledge.

All I can restate is that optimal diffraction will occur when the slit width is within one order of magnitude of the wavelength.

9. ### m25

304
19
May 28, 2014
Ah, so we get optimal diffraction as long as slit size and wavelength are not TOO different?(i.e. by one order of magnitude)
So if the wavelength gets bigger than slit by one magnitude, that's when the wavelength can no longer get through the slit?