but that will b too long na...???
some tips for smaller calculations??
If wavelength of photon is 2.2 * 10^{-11} m, h = 6.6 * 10^{-34} J-sec, then momentum of photon is
E=hk, where k is the frequency, E is the enrgy, from where u can get the momentum.
another one
If electron falls from n = 3 to n = 2, then emitted energy is
yup first u find E then use relation
p = h√2mE
i thnk that will do [1]