Lecture 25: Elementary Processes in QED (II)

TL;DR

Compton scattering is the process of a photon interacting with an electron, resulting in the photon being scattered with a different frequency. This effect can be used to detect the location of galaxy clusters.

Transcript

[SQUEAKING] [RUSTLING] [CLICKING] PROFESSOR: So let's start. So let me just clarify one question, which was asked last time. So when we calculate the total cross-section for, say, for this e plus e minus to mu plus, mu minus, then we find that there's a funny fact -- yeah, let me just write down-- so then there's a factor like this. m prime square ... Read More

Key Insights

• 💱 Compton scattering occurs when a photon interacts with an electron, resulting in a change in the photon's frequency.
• 🦾 Classical electrodynamics predicts elastic scattering, while quantum mechanics shows that inelastic scattering occurs.
• 😘 In the rest frame of the electron, the frequency of the scattered photon remains the same when the initial photon has low energy.

Questions & Answers

Q: What is Compton scattering?

Compton scattering is the process in which a photon interacts with an electron, resulting in a change in the photon's frequency.

Q: How does the scattering differ between classical electrodynamics and quantum mechanics?

In classical electrodynamics, elastic scattering is predicted, while quantum mechanics shows that inelastic scattering occurs, with the photon losing energy and the electron gaining energy.

Q: What happens to the frequency of the photon in the rest frame of the electron?

When the initial photon has low energy, the frequency of the scattered photon remains the same in the rest frame of the electron.

Q: What is inverse Compton scattering?

In inverse Compton scattering, a high-energy electron transfers its energy to a low-energy photon, resulting in the photon gaining energy and the electron losing energy.

Summary & Key Takeaways

• Compton scattering is a process in which a photon interacts with an electron, causing the photon to change frequency.

• The scattering can be explained using classical electrodynamics, which predicts elastic scattering. However, quantum mechanics shows that inelastic scattering occurs, with the photon losing energy and the electron gaining energy.

• In the rest frame of the electron, the frequency of the scattered photon remains the same when the initial photon has low energy, while in the inverse Compton scattering process, a high-energy electron can transfer its energy to a low-energy photon.