The rest energy of an electron and its antiparticle, a positron, ...

[Tazate]

The rest energy of an electron and its antiparticle, a positron, is 0.511 MeV. In order to produce an electron-positron pair, a gamma ray must have an energy larger than 1.022 MeV because of
 a. time dilation
  b. length contraction
  c. the equivalence of mass and energy
  d. the principle of relativity
  e. none of the above

Question 2

When it comes near a heavy nucleus, a gamma ray, which is a high energy photon, can disappear, and in its place there will be produced an electron and a positron, which both have mass. This pair production is an example of
 a. time dilation
  b. length contraction
  c. the equivalence of mass and energy
  d. the principle of relativity
  e. none of the above

[komodo7]

Answer to Question 1

C

Answer to Question 2

C

[Tazate]

Both answers were spot on, thank you once again

[komodo7]

Great! Please up vote