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Diffraction
Intermediate
Bending of waves around obstacles and through gaps.
Waves spread when passing through gaps or around edges. The effect is strong when the gap is comparable to the wavelength.
You hear someone round the corner but can't see them: sound λ ≈ 1 m, light λ ≈ 500 nm.
Narrower slit gives more spreading.
In more detail
Diffraction is the spreading of a wave as it passes through an opening or around an obstacle. It is strongest when the gap size is comparable to the wavelength.
Real-world uses
- You can hear sound around corners because low frequencies diffract strongly.
- X-ray diffraction reveals crystal structures.
- Sound carries around a corner into a room, and radio waves reach behind hills, because waves spread out after passing an obstacle.
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Frequently asked questions
Why does diffraction depend on wavelength?
Because a wave spreads significantly only when the obstacle is close to its wavelength in size.
Does light diffract?
Yes, but for visible light the effect is small unless the openings are very small.
Does diffraction depend on wavelength?
Yes. Waves spread more when the gap or obstacle is comparable to their wavelength, which is why low notes carry further.
Related topics in Waves & Sound
Reflection of waves · Phase change on reflection · Refraction of waves · Principle of superposition · Constructive and destructive interference · Path difference and phase