When an atom emits a photon, the atom's mass
A) decreases slightly.
B) increases slightly.
C) remains exactly the same.
D) could do any of the above.
E) becomes negative-- i.e., less than zero.

Question

Quizplus · Accepted Answer

When an atom emits a photon, it loses energy. According to the mass-energy equivalence principle (E=mc^2), this loss of energy corresponds to a slight decrease in mass.

When an Atom Emits a Photon, the Atom's Mass