# Compton Effect

If the maxmimum energy imparted to an electron in Compton scattering is 45 keV what is the wavelength of the incident photon?

So a compton scattering happens and the energy is 45 keV and I need to find the wavelength of the photon incident to this electron. I think I need to use

Lambda = h/mc (1-Cos), but I am not given an angle.

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OlderDan
Homework Helper
Jacob87411 said:
If the maxmimum energy imparted to an electron in Compton scattering is 45 keV what is the wavelength of the incident photon?

So a compton scattering happens and the energy is 45 keV and I need to find the wavelength of the photon incident to this electron. I think I need to use

Lambda = h/mc (1-Cos), but I am not given an angle.
Maximum energy corresponds to (minimum/maximum, you decide) wavelength change? Which angle gives the (minimum/maximum) wavelength change?

Your equation is missing something. It is not quite correct in two places. For one, the angle for the cos is missing. What else?

Last edited:
jtbell
Mentor
Imagine you're playing billiards. You shoot the cue ball (photon) against the eight-ball (electron), with a certain amount of energy. What direction does the cue ball go after the collision, when it transfers the maximum amount of energy to the eight-ball?

The cue ball will go in reverse fro mthe way it came?

OlderDan
Homework Helper
Jacob87411 said:
The cue ball will go in reverse fro mthe way it came?
Yes, although in the case of a cue ball that has no backspin there is no rebound because the masses of the balls are the same. But if you had a cue ball of lesser mass, it would bounce back. And if you had a cue ball of greater mass, it would keep going forward in a stratight line when the maximum energy is transferred.

So there is the collision and there is no rebound, but the 8 ball (electron) does go forward and now has the energy from the cue ball (photon)

correct! they have the same masses, so the cue ball transfers all of its energy to the eightball making it move forward and the cue ball come to a halt.

jtbell
Mentor
Bleah, I forgot about the mass considerations... with equal masses and if topspin doesn't come into play, the cue ball simply comes to a dead stop in a head-on collision with a stationary eight-ball.

I should have specified something like a ping-pong ball hitting the eight-ball. After all, the photon is massless.

OlderDan