Diffraction and Interference (Light)
- 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) and the wavelength of the wave (λ) are of the same order (a ~ λ).
- 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.
- 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.