When electron and proton are accelerated through the same potential difference which one has greater de Broglie wavelength?

Monochromatic light of wavelength 632.8 nm is produced by a helium-neon laser. The power emitted is 9.42 mW.

a.) Find the energy and momentum of each photon in the light beam. 

c.) How fast does a hydrogen atom have to travel in order to have the same  momentum as that of the photon?

Given,
Wavelength of monochromatic light, λ = 632.8 nm = 632.8 x 10–9

 m
∴ Frequency, v = cλ = 3 × 108632.8 × 10-9Hz 

                                 = 4.74 × 1014Hz

(a) Energy of a photon, E = hv

                                       = 6.63 × 10-34× 4.74 × 1014J= 3.14 × 10-19J.

Momentum of each photon, p (momentum) = hλ                            = 6.63 × 10-34632.8 × 10-9                              = 1.05 × 10-27 kg ms-1 

(b) Power emitted, P = 9.42 mW = 9.42 x 10–3 W
Now, P = nE  

n = PE = 9.42 × 10-3W3.14 × 10-19J                = 3 × 1016 photons/sec. 

(c) Velocity of hydrogen atom 

                  v = 1.05 × 10-271.673 × 10-27ms-1   

                    = 0.63 ms-1.