Here’s the key difference between diffraction and refraction:
- Diffraction is the bending and spreading of light waves when they encounter an obstacle or pass through a narrow opening. It causes light to spread out and create interference patterns, especially when the obstacle size is comparable to the wavelength of light. Diffraction explains phenomena like the spreading of light around edges and the patterns seen in single-slit experiments.
- Refraction is the change in direction of light waves as they pass from one medium to another with a different optical density (like air to water). This bending occurs because light changes speed when entering a new medium. Refraction explains effects like the bending of a straw in a glass of water or the focusing of light by lenses.
In short:
- Diffraction involves light bending around edges and spreading out.
- Refraction involves light bending at the boundary between two different materials because of a speed change.
Both are wave behaviors but occur in different situations and for different reasons.