Question

Calculate the mass of a photon of sodium light having wavelength 5894 A 0 & velocity as 3 10 8 ms - 1

Answer 1

"Wavelength=h/mv

so m=h/(wavelength*velocity)

=6.6*10^34/{[5894*10^(-10)]*3*10^8}

on solving we get

m=0.000373*10^(-32)

l = h / mc. l stands for wavelength

So m = h / c l

Hence m = 6.626*10^-34 / 3*10^8 * 589*10^-9

So m = 3.75*10^-36 kg

Compare this with atomic mass unit which is of the order of 10^-27

Hence mass of photon is not considerable

"