Diffraction and scattering are both phenomena involving the interaction of waves or particles with obstacles or particles, but they describe different processes.
At a fundamental level, the key difference lies in how the interaction occurs and what is being affected:
- Diffraction primarily describes the bending of waves around obstacles or openings.
- Scattering typically describes the deflection of waves or particles due to localized interactions or collisions with other particles or objects.
Understanding the Concepts
Diffraction
According to Collins' Dictionary, diffraction is defined as 'a deviation in the direction of a wave at the edge of an obstacle in its path'.
This phenomenon is a characteristic property of waves. When a wave encounters an edge, a slit, or an obstacle comparable in size to its wavelength, it doesn't just stop or cast a sharp shadow. Instead, the wave bends and spreads out into the region behind the obstacle or beyond the opening.
Examples of Diffraction:
- Light spreading out after passing through a narrow slit.
- Sound waves bending around a corner, allowing you to hear sounds from another room.
- The pattern created when light reflects off the grooves of a CD or DVD.
Scattering
Collins' Dictionary defines scattering as 'the process in which particles, atoms, etc., are deflected as a result of collision.' The word scatter can also be a noun denoting the act of scattering. While this definition focuses on particles, scattering also applies to waves being deflected by interactions with other particles or objects.
Scattering involves an interaction where the wave or particle is deflected from its original path. This can be due to reflection, refraction, or absorption followed by re-emission in a different direction. The interaction is often with multiple small obstacles or irregularities within a medium.
Examples of Scattering:
- Why the sky is blue: Sunlight (short wavelengths) is scattered more effectively by gas molecules in the atmosphere than longer wavelengths (like red).
- Why clouds are white: Water droplets in clouds scatter all wavelengths of light roughly equally.
- Rutherford scattering: Alpha particles being deflected by atomic nuclei.
- Light reflecting off a rough surface, causing diffuse reflection.
Key Distinctions Summarized
Here's a comparison highlighting the main differences:
| Feature | Diffraction | Scattering |
|---|---|---|
| Collins' Definition | "deviation in the direction of a wave at the edge of an obstacle" | "process in which particles... are deflected as a result of collision" (also applies to wave deflection) |
| Primary Phenomenon | Bending and spreading of waves | Deflection of waves or particles |
| Interaction With | Edges, slits, or obstacles/apertures comparable to wavelength | Localized particles, atoms, molecules, or irregularities |
| Nature of Affected Entity | Primarily describes wave behavior | Describes both wave and particle behavior |
| Outcome | Wave fronts deviate, creating interference patterns (often) | Energy or momentum is redirected in various directions |
In essence, diffraction is about a wave's inherent ability to bend around things, while scattering is about an interaction (like a collision or reflection) that causes a wave or particle to bounce off or change direction.
