Let m represent the mass of an electron, and c represent the ...

[MGLQZ]

Let m represent the mass of an electron, and c represent the speed of light. In order to create an electron-positron pair, we must start with a photon whose energy is
 
  A) at least mc2.
  B) at least 2mc2.
  C) at least 4mc2.
  D) any value greater than zero.
  E) Actually it is impossible to create such pairs from photons.

Question 2

The two great theories of 20th-century physics are quantum theory and
 
  A) the theory of relativity.
  B) thermodynamics.
  C) Hamiltonian mechanics.
  D) the bootstrap theory of elementary particles.
  E) electromagnetism.

[chloejackso]

Answer to Question 1

B

Answer to Question 2

A

[MGLQZ]

Excellent

[dyrone]

TYSM