# Direction of a photon created by bremsstrahlung radiation?

1. Aug 3, 2013

### iScience

basically any time i have an arc, i have electrons flowing in the opposite direction to the field gradient. so when the electrons reach the other side, they will be stopped, which will then produce an EM wave. In, class, my professor drew the direction of radiation in a particular direction, but the electrons deccelarating should produce a wave radially in all directions shouldn't it? with the max amplitude being in the plane normal to the velocity? ie, the charge carrier's direction of travel?
so why would it the bremsstrahlung process emit radiation in only one particular direction?

2. Aug 3, 2013

### voko

Wikipedia has a page on bremsstrahlung, which describes the angular distribution.

3. Aug 4, 2013

### iScience

i ddn't understand any of the math behind angular distribution, but i assume the existence of the 'distribution' implies that radiation is indeed emitted radially?

4. Aug 4, 2013

### voko

I am not sure what "radially" means here. In the initial description, electrons collide with "the other side", presumable the anode, so their motion at that time is mostly linear. In that case, the second formula in the section on angular distribution applies. The most important part of that formula is $$\frac { \sin^2 \theta } {(1 - \beta \cos \theta)^5}$$

where $\theta$ is the angle between the direction of motion and the direction of observation, and $\beta = v/c$, the ratio of the velocity with the speed of light. It can be seen immediately that there is no emission along the line of motion, and that there is a maximum, the direction of which depends on the initial velocity.