momentum
posted by Tiffany .
do gamma rays carry momentum? i thought they don't because they don't have mass so mv=0 but my frend says even tho they don't have mass they still carry momentum. how does this make sense? please help.

Photons in general carry momentum so any electromagnetic wave has momentum associated with it despite its lick of rest mass in the classical sense. If a photon hits something, it moves it.
E = energy of photon = m c^2 = h f where c is velocity of light and h is plank constant and f is the frequency
Of course we know classical rest mass m is zero but that does not prove there is no energy, m c^2 at the velocity of light.
then m c = momentum p
but m c = E/c
so p = E/c
but E = h f
so
momentum p = h f /c
but f/c = 1/Tc = 1/Lambda
where T is period and Lambda is wavelength
so
p = h/Lambda