Question

Calculate the wavelength of a proton with energy 2.45 eV. what's different between proton and photon formula? can anyone tell me? thank you

Answer 1

Are you sure you are going to calculate the energy of a proton and not a photon?
A "proton" is atomic materiale. a "photon" however is a light particle and can for an example be admitted when an electron falls to a lower energy state.

Answer 2

one formula (planck's) is for massless particles (i.e. photons) the other (deBroglie's) is for things with mass...

so, for this question, find the velocity, v, of the particle:

\[K.E.=\frac{ 1 }{2 }mv ^{2}\]

then use the deBroglie equation:

\[\lambda=\frac{ h }{ mv }\]

wavelength is in meters, velocity in m/s, mass in Kg.