e=mc2

[ceenik]

the celebrated equation E=mc2 or m=E/c2 (c is the speed of light) tells us how much mass is loss, m, must be suffered by a nuclear reactor in order to generate a given amount of energy, E/ Which of the following statements is correct?

a)The same equation, E=mc2 or m=E/c2, also tells us how much mass loss, m, must be suffered by a flashlight battery when the flashlight puts out a given amount of energy, E.

b) The equation E=mc2 applies to nuclear energy in a reactor, but not to chemical energy in a battery.

[Astronuc]

Why would either be true? or Why would E=mc2 be true for a nuclear reaction, but not true for a chemical reaction. Nuclear reactions usually involved energies in the MeV range, while chemical reaction energies are in the eV range.

[Andrew Mason]

Einstein developed E=mc^2 without knowing anything about the nucleus. His paper published in 1905 predated Rutherford's discovery of the nucleus by about six years. In his original paper (http://www.fourmilab.ch/etexts/einstein/E_mc2/e_mc2.pdf), Einstein showed that any object emitting/absorbing light of energy L will lose/gain mass in the amount m = L/c^2. I think that should tell you the answer to the question.

AM