A gamma-ray photon is back scattered at an angle of 180° after a collision with an electron.If the scattered photon has energy 150 keV,what was the energy of the initial photon?
A)303 keV
B)363 keV
C)95 keV
D)427 keV
E)393 keV

Question

Quizplus · Accepted Answer

In Compton scattering, the scattered photon's energy is given by,
E' = E/(1 + (E/Mc^2)*(1 - cos(theta))),
where E is the initial photon energy, E' is the scattered photon energy, theta is the scattering angle, M is the rest mass of the electron, and c is the speed of light.

Since the photon is backscattered (theta = 180), we have cos(theta) = -1, and solving for E we get,
E = E'/(1 - (E'/Mc^2)).

Substituting the given values, we get E = 363 keV. Therefore, the initial photon energy was 363 keV.

Hence, the correct choice is B.

A Gamma-Ray Photon Is Back Scattered at an Angle of 180°