- #1

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## Homework Statement

Find the mass of photon in motion.

## Homework Equations

E=hf

p=hf/c

## The Attempt at a Solution

I just started studying modern physics and am aware of the above two equations. However equating E to 1/2mv^2 gives a different (wrong) answer while equating p to mv gives the correct expression when we consider v=c; is it wrong to write E=1/2 mv^2 or p=mv for a photon (something to do with relativity perhaps)?

I'd appreciate some insights, thank you