Diffraction and Interference (Sound)

Summary

• Diffraction…
  • is the bending or spreading of a wave around an obstacle or through an opening.
  • is most apparent when the size of the obstacle or opening (a) is on the same order as the wavelength of the wave (λ).
• Sound vs. Light
  • Sound waves are millions of times longer than light waves.
  • Diffraction is more easily observed for sound than light in everyday experience.
  • You can hear around corners, but you can't see around them.
  • Light sources cast noticeable shadows.
• A shadow is a region behind an obstacle into which a wave does not easily diffract.
  • Umbra: a region of total shadow; the source of the wave is completely obscured.
  • Penumbra: a region of partial shadow; the source of the wave is partially obscured.