Compton effect

Definition

The Compton effect is the increase in wavelength (or decrease in energy) of X-rays or gamma rays when they are scattered by electrons. This phenomenon demonstrates the particle nature of light and supports the concept of photon momentum.

5 Must Know Facts For Your Next Test

1. The Compton effect was discovered by Arthur H. Compton in 1923.
2. It provides evidence for the dual nature of light, showing that photons have both wave-like and particle-like properties.
3. The change in wavelength is given by the equation $\Delta \lambda = \frac{h}{m_e c} (1 - \cos \theta)$, where $\Delta \lambda$ is the change in wavelength, $h$ is Planck's constant, $m_e$ is the electron rest mass, $c$ is the speed of light, and $\theta$ is the scattering angle.
4. The Compton shift depends on the angle at which photons are scattered; a larger angle results in a greater increase in wavelength.
5. This effect cannot be explained by classical wave theory and requires quantum mechanics to be fully understood.

Review Questions

• What does the Compton effect demonstrate about the nature of light?
• How does the scattering angle affect the change in wavelength during the Compton effect?
• Write down and explain the equation describing the change in wavelength ($\Delta \lambda$) for a photon undergoing Compton scattering.

Related terms

Photon: A quantum of electromagnetic radiation with zero rest mass and energy given by $E = h\nu$, where $h$ is Planck's constant and $\nu$ is frequency.

Electron Rest Mass: The mass of an electron at rest, approximately $9.109 x 10^{-31}$ kilograms.

Planck's Constant: $6.626 x 10^{-34}$ Js, a fundamental constant used to describe quantized energy levels.