According to Einstein E²=(mc²)²+(pc)². In the case of photons m would be equal to zero since photons are massless, so the equation simplifies to E²=(pc)². p represents momentum but because p=mv and mass is still zero, p would also be zero. Therefore E should also be equal to zero, but this doesn’t make sense since light must have energy (eg. solar energy). I hope I’ve explained my thoughts clearly and thanks to anyone who can help me understand.
In: Physics
You’re conflating relativity with Newtonian mechanics, Newtonian Mechanics is a good approximation of how things work but it’s just an approximation. P=mv is from Newtonian mechanics and thus isn’t applicable here.
The correct eqation is E² = m₀²c⁴+p²c², and since m₀ = 0, E=pc.
The energy of a photon is E = hc/λ where h is Planck’s constant, c is the speed of light, and λ is the wavelength.
Therefore pc = hc/λ which becomes p=h/λ (Momentum = Planck’s Constant / wavelength)
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