Compton Scattering - Find x component of electron momentum

[JoeyBob]

Homework Statement

See attached

Relevant Equations

p=h/wavelength

So I can find the initial momentum using p=h/wave = 4.98 x 10-23. Now my problem is that I don't know the final momentum of the photon nor electron, I just know the photon is scattered at an angle of 34 degrees.

I know how to solve this problem if I was given the final wavelength of the light, but that's not given.

p initial = cos(34)* mag. of photon momentum + x component of electron momentum

From the above equation all I need is the final magnitude of the momentum of the photon. Since the final wavelength is not given idk how to find this. If the velocity or kinetic energy of the electron was given I could use energy conservation to find the answer, but that's not given either.

I just don't understand how to calculate the final momentum of the photon if no final wavelength is given.

 

[Steve4Physics]

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I just don't understand how to calculate the final momentum of the photon if no final wavelength is given.

Have you solved this yet? If not, see the formula you stated in post #7 in your other thread: https://www.physicsforums.com/threads/compton-scattering-determine-momentum.1001734/

Also, you can easily avoid losing marks in exams/assignments by including the correct units with values. For example to state a momentum is '4.98 x 10-23' is incomplete: is that in units of g.cm/s, or lbs.ft/s, or something else?

 

[JoeyBob]

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Have you solved this yet? If not, see the formula you stated in post #7 in your other thread: https://www.physicsforums.com/threads/compton-scattering-determine-momentum.1001734/

Also, you can easily avoid losing marks in exams/assignments by including the correct units with values. For example to state a momentum is '4.98 x 10-23' is incomplete: is that in units of g.cm/s, or lbs.ft/s, or something else?

I mean I thought I understood it since I was able to use momentum or energy to solve the problem you cite in that thread. The issue here is I don't have the final wavelength so nothing seems to work.

Units are what I use as a last resort and don't always help. Trying to cancel them out units to give the units of the answer ect.

 

[Steve4Physics]

I mean I thought I understood it since I was able to use momentum or energy to solve the problem you cite in that thread. The issue here is I don't have the final wavelength so nothing seems to work.

Units are what I use as a last resort and don't always help. Trying to cancel them out units to give the units of the answer ect.

In post #7 of https://www.physicsforums.com/threads/compton-scattering-determine-momentum.1001734/ you wrote “change in wavelength = (h/mc)(1-cos(angle)”.

You got the brackets wrong, but you can sort this out.

Use your formula to find the change in wavelength. Then add this to the initial wavelength. This gives you the final wavelength.

Units are not ‘a last resort’. It is incorrect to state a value without correct units. Like saying “This piece of string is 15 long”. Also, it creates a very poor impression when someone sees it - and it will cost you marks in examinations. Your decision!

Edit. I don't mean puitting units into equations. I mean including the units when stating single values.