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Monday, November 28: Comptonization
When photons and electrons coexist in the same volume of space, their scattering interactions can transfer energy from photons to electrons (Compton scattering) or from electrons to photons (inverse Compton sca

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Monday, November 21: Inverse Compton Scattering
When I did the calculations for the scattering of photons from electrons, I chose (for the sake of simplicity) the inertial frame of reference in which the electron was initially at rest. However, a

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Wednesday, November 16: Return of Synchrotron
Both bremsstrahlung and synchrotron radiation can be emitted by hot ionized gas. How can you tell whether the light you observe from a distant galaxy is bremsstrahlung or synchrotron? One way of disti

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Monday, November 7: Synchrotron Radiation for Beginners
An accelerated electron emits electromagnetic radiation. The most effective way to accelerate an electron is to use electromagnetic forces. Since electrons have mass, they can also be accele

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Monday, October 31: Relativistic Charged Particles
As I was saying, before the midterm exam intervened, in an inertial frame of reference K there exists an electric field E and a magnetic field B at a spacetime location (r, t). Another inertial f

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ASTRONOMY 822: Electromagnetic Radiation
Problem Set 4: due Wednesday, October 26
1) Commercial radio stations often broadcast their programs using 2 to 12 dipole antennas arranged in long rows:
a) Why do they use this arrangement, rather th

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Monday, October 10: Potentials
I've already remarked on the similarity between the electrostatic force between two point charges, q1 q2 (1) F = 2 , r and the gravitational force between two point masses, F = -G m1 m2 . r2 (2)
The similarities be

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Monday, September 26: Radiative Transfer
As light travels through the universe, things happen to it. By interacting with charged particles, photons can gain energy; they can lose energy; they can change their direction of motion. Photons can also

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Monday, October 17: Multi-particle Systems
For non-relativistic charged particles, we have derived a useful formula for the power radiated per unit solid angle in the form of electromagnetic radiation: dP q2 2 2 [a sin ] , = d 4c3 q (1)
where q

AST 822: Electromagnetic Radiation
Problem Set 5: due Wednesday, November 9 1) An observer in the inertial frame of reference K sees a particle moving in the xy plane, with velocity ux = u cos and uy = u sin . The inertial frame of reference K is mo

AST 822: Electromagnetic Radiation
Problem Set 6: due Wednesday, November 23 1) A highly relativistic electron initially has Lorentz factor 0 1. It is moving in a magnetic field of constant flux density B with a pitch angle . What is (t) as the elect

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Wednesday, September 21: Introduction
This course deals with continuum radiation processes of astrophysical interest. (Processes that produce spectral lines, rather than continuum radiation, are dealt with in Astronomy 823: Theoretical Spectrosco

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Monday, October 3: Stellar Atmospheres
There exist entire books written about stellar atmospheres; I will only give a brief sketch of the simplest approximations used in studying stellar atmospheres. In particular, I want to discuss that most use

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Monday, October 24: Special Relativity Review
Personally, I'm very fond of classical physics. As we've seen recently, you can derive some very useful electromagnetic formulae without taking into account quantum mechanics or special relativity. Ho

ASTRONOMY 822 Electromagnetic Radiation
Problem Set 1 due Wednesday, October 5 at class time
1) If you could construct a box opaque to neutrinos, then at a temperature T , the thermal neutrinos inside the box would have the specific intensity I (T )

ASTRONOMY 822 Electromagnetic Radiation
Problem Set 3 due Wednesday, October 19 at class time 1) A particle of charge q is moving at a constant speed v q along a straight line. You are located so that the particle's distance at closest approach is b

ASTRONOMY 822 Electromagnetic Radiation
Problem Set 2 due Wednesday, October 12 at class time 1) Consider a plane electromagnetic wave of the form E = ey E0 cos(kx - t) ^ and B = ez E0 cos(kx - t) . ^ The wavelength of the light is measured to be =