Photon–Particle Collisions
The Compton effect and momentum carried by photons
|
Check Your Understanding
5 quick questions — pick an answer to see if you’re right.
1. The Compton effect shows that light acts like particles when it…
2. After an X-ray photon collides with an electron, the photon's energy and momentum…
3. Which color of visible light has photons with the greatest momentum?
4. Find the momentum of a photon with wavelength 6.63 × 10⁻⁷ m. (h = 6.63 × 10⁻³⁴ J·s)
5. In a photon–electron collision, which quantities are conserved?
X-Rays Bouncing Off Electrons
In 1923, Arthur Compton fired X-ray photons at a target. Some X-rays scattered off electrons, and the scattered X-rays had a longer wavelength than the incoming X-rays. The struck electrons recoiled.
Which explanation is consistent with Compton’s results?
▶ Want a challenge? Open 6 more Regents-style questions (harder · mixed formats)
Challenge score: 0 / 6
C1. In one trial, the incoming X-ray photons have a wavelength of 7.10 × 10−11 m. Substitute numerical values into a mathematical representation that can be used to determine the energy of one incoming photon. Then calculate the energy. (h = 6.63 × 10−34 J·s; c = 3.00 × 108 m/s)
C2. Which quantity of the photon decreased after the collision?
C3. A student makes the following claim.
Place a check mark in either the Support or Refute box. Justify your response using a mathematical relationship.
C4. An X-ray photon (λ = 7.10 × 10−11 m) moving to the right strikes an electron at rest and scatters straight back to the left with λ = 7.59 × 10−11 m. Choose the direction of the electron’s recoil momentum, and determine its magnitude. (p = h/λ) Enter the number that goes in front of × 10−23 kg·m/s.
●
C5. Which conservation laws apply to the photon–electron collision?
C6. The largest possible Compton wavelength shift is about 4.9 × 10−12 m, no matter what the incoming wavelength is. Explain why Compton used X-rays (λ ≈ 10−10 m) instead of visible light (λ ≈ 5 × 10−7 m) to observe the effect.