Why does wavelength affect diffraction?

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SUMMARY

The discussion centers on the relationship between wavelength and diffraction, emphasizing that longer wavelengths bend more easily around obstacles. Participants clarify that this principle applies universally to all types of waves, including electromagnetic waves like light and longer wavelengths such as radio waves. The analogy of ocean waves bending around obstacles effectively illustrates this concept, reinforcing the understanding that the size of the obstacle relative to the wavelength determines the extent of diffraction.

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  • Understanding of wave mechanics
  • Familiarity with electromagnetic waves
  • Basic knowledge of diffraction principles
  • Concept of wavelength in physics
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  • Research the mathematical models of diffraction, specifically Huygens' Principle
  • Explore the differences in diffraction patterns between water waves and electromagnetic waves
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Students and professionals in physics, optical engineers, and anyone interested in the principles of wave behavior and diffraction in various mediums.

atyy
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This question came up in the biology section
https://www.physicsforums.com/threads/explain-different-types-of-light-microscopy.833990/.

Q1: The longer the wavelength of a wave, the more easily it bend around an obstacle. I do understand the mathematics, but is there any intuition for it?

Q2A: Is this an acceptable explanation, or is it misleading?

"If light were fundamentally a ray, then it makes sense that it would travel in straight lines. But if you think light is a wave, then it makes sense that it would not travel in straight lines. After all, if you put an obstacle in the path of waves in the sea, the waves can go around the obstacle. The bigger the obstacle, the less the waves can go around it. On the other hand, the bigger the wavelength, the smaller the obstacle is relative to the wave, so this gives some intuition as to why wavelength affects bending around an obstacle."

Q2B: If the above is acceptable, is it acceptable for all wave diffraction, or only for some, eg. ok for water waves or air, but not for electromagnetic waves?
 
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atyy said:
Q2A: Is this an acceptable explanation, or is it misleading?

"If light were fundamentally a ray, then it makes sense that it would travel in straight lines. But if you think light is a wave, then it makes sense that it would not travel in straight lines. After all, if you put an obstacle in the path of waves in the sea, the waves can go around the obstacle. The bigger the obstacle, the less the waves can go around it. On the other hand, the bigger the wavelength, the smaller the obstacle is relative to the wave, so this gives some intuition as to why wavelength affects bending around an obstacle."

Sure, that's acceptable. Light is just a really short wavelength EM wave, so if you think about long-wavelength radio waves, they do indeed diffract around everyday objects.

atyy said:
Q2B: If the above is acceptable, is it acceptable for all wave diffraction, or only for some, eg. ok for water waves or air, but not for electromagnetic waves?

It should apply to all types of waves.
 

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