Why wavelength matters in diffraction

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Homework Help Overview

The discussion revolves around the significance of wavelength in the context of diffraction, particularly in relation to openings of varying sizes. The original poster uses an example involving waves passing through a 10-centimeter opening to prompt questions about the effects of different wavelengths on diffraction phenomena.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the relationship between wavelength and the size of openings, questioning why diffraction occurs significantly when wavelengths are comparable to opening sizes. They inquire about the implications of long versus short wavelengths in diffraction scenarios.

Discussion Status

The discussion is active, with participants sharing observations and questioning the conditions under which diffraction is significant. Some have provided insights into the relationship between wavelength and opening size, while others express curiosity about specific examples and rules of thumb related to diffraction.

Contextual Notes

Participants note that diffraction is not significant when the wavelength is much shorter than the opening size, as illustrated by the example of walking through a doorway. There is an emphasis on the need for careful consideration of the scale of the opening relative to the wavelength for diffraction effects to be observed.

MIA6
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Waves pass through a 10.-centimeter opening in a barrierr without being diffracted. This observation provides evidence that the wavelength of the waves is much shorter than 10. cm. This is a multiple-choice question, and this is not the question that I am asking. I want to use this as an example to ask that why wavelength matters in diffraction, like in slit problem. If the wavelength is long, then what happens? If it is short, then?
thanks.
 
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Diffraction is only significant if the wavelength is similair to the size of the opening. So light diffracts through a pinhole or small slit, electrons diffract in a crystal, water waves diffract in a harbour.

But you don't significantly diffract when walking through a doorway!
 
mgb_phys said:
Diffraction is only significant if the wavelength is similair to the size of the opening.

But you don't significantly diffract when walking through a doorway!

But why?:blushing:
 
While the same amount of light is effected by the edges,
whether it is a 100 nm opening or a 100 mm opening,
the amount of light that is NOT effected is much greater
for the wider opening.
Rule-of-thumb says that "about 1 wavelength wide"
is *markedly* effected by a single sharp edge ...
so the fraction 2*600 [nm]/100,000,000 [nm] IS effected.
It takes _serious, careful_ work to notice 10 parts per million
(but it can be done ... just wait till next year!)
 

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