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aurora14421
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Homework Statement
An atom initially at rest emits a photon with frequency f. Explain why the mass of the atom decreases, and by an amount greater than hf/c^2.
Homework Equations
E= mc^2
E = hf
The Attempt at a Solution
So I know that the atom must lose mass when the photon is emitted because in order for it to emit energy it must lose mass (by E = mc^2), but I don't understand why it should be more than hf/c^2, since from these 2 equations:
E = mc^2 = hf
therefore m = hf/c^2
Why is this wrong?
Thanks.