Important

Question 1

Thomson Scattering Description

Answer 1

Radiation in an electric and magnetic field produced
by a moving (Δv«c) charge.

Thomson scattering is the elastic scattering of electromagnetic radiation by free charged particles, such as electrons. It occurs when the electric field of incident radiation interacts with the charged particle, causing it to oscillate and re-emit radiation at the same frequency but altered direction.

Question 2

Thomson Scattering Process

Answer 2

1) Stationary q in inertial frame at t=0
2) Small acceleration to Δv in Δt, then const velocity
3) After t, consider sphere radius r=ct :

• Outside sphere/medium:
  field lines do not yet know that charge has moved à radial to the
  charge
• Inside sphere/medium:
  field lines radial in reference frame of moving charge
• between the two:
  thin shell cΔt where the lines join u

Question 3

Tangential (or transverse) electric field

Answer 3

Radiation is null towards the observer but is max perpendicular to it (cuz of values of theta with sine and cosine).

• for observers POV, all visible acceleration is perp to line of sight & contributes to the radiated E field
• the invisible acceleration compenent is parallel to the line of sight

Far from the charged particle only E(θ) will contribute to the radiation field.

E(θ) is proportional to 1/r
E(r) is proportional to 1/r^2

Result: Energy loss from accelerated charged particle

Question 4

Poynting Vector

Answer 4

Gives the energy flux radiated in each direction (basically energy flux of EM field)

Question 5

Larmor’s Formula

Answer 5

Describes the power radiated by an accelerating charged particle.
- need to know what/where the energy flux is in each direction using Poynting vector
- is the basis for free-free and synchrotron emission

Question 6

How to use Larmor’s Formula

Answer 6

Proportional to square of the acceleration (acceleration is usually
proportional to charge/mass ratio) – radiation electron vs proton
* It is nonrelativistic
* Does not consider quantum mechanics (it fails at atomic level)

Question 7

Bremsstrahlung Basics

Answer 7

AKA breaking radiation AKA free-free emission because the radiation corresponds to transitions between unbound states in nucleus field

Radiation emitted in the encounter between an e- and a nucleus.

Three types:
* Single electron Bremsstrahlung
* Thermal Bremsstrahlung
* Relativistic Bremsstrahlung