# How much total kinetic energy will an electron-position pair have if produced by a photon of energy 1.48 MeV? Answer in units of MeV. How would I do this? thx.

## To calculate the total kinetic energy of an electron-position pair produced by a photon, you can use the conservation of energy principle. The energy of the photon will be converted into the rest mass energy of the electron-position pair (which is twice the rest mass energy of an electron or positron) and the kinetic energy of the pair.

Here's how you can calculate it:

1. Start by converting the given photon energy from MeV (mega-electron volts) to joules, as energy should be in SI units for this calculation. 1 MeV is equal to 1.6 × 10^-13 joules. Therefore, 1.48 MeV is equal to 1.48 × 1.6 × 10^-13 joules.

2. Next, use Einstein's mass-energy equivalence equation, E = mc^2, to find the rest mass energy of the electron-position pair. The rest mass energy, E, is given by the equation E = 2mec^2, where me is the rest mass energy of an electron or positron (0.511 MeV).

The rest mass energy of the electron-position pair is therefore:
E_rest = 2 × 0.511 MeV.

3. Subtract the rest mass energy of the electron-position pair from the given photon energy to find the kinetic energy of the pair.

Kinetic energy, KE = Photon energy - Rest mass energy
= (1.48 MeV × 1.6 × 10^-13 J/MeV) - (2 × 0.511 MeV × 1.6 × 10^-13 J/MeV)

4. Calculate the result for the kinetic energy.

KE = (1.48 × 1.6 × 10^-13 J) - (2 × 0.511 × 1.6 × 10^-13 J)
= Result in joules

5. Finally, convert the result back to MeV by dividing by 1.6 × 10^-13 J/MeV.

Result in MeV = (Result in joules) / (1.6 × 10^-13 J/MeV).

By following these steps, you can calculate the total kinetic energy of the electron-position pair.