Verified answer

First, use the Einstein equation E = mc^2 to obtain the energy of the proton.

E = (1.673 x 10 ^ -27) (2.83 x 10 ^ 4) ^2

= 1.3399 x 10 ^ -18 J

= 8.363 eV

Then equal the energy to E = hf = hc/ lamda.

Where lamda is the Broglie wavelength.

lamda = (hc) / (1.3399 x 10 ^ -18)

= 1.484 x 10 ^ -7 m

according to de Broglie,

l=h/p=h/mv

where l=wavelength

h=Planck's constant with value 6.626*10^-34 Js.

p=momentum of particle which in turn is equal to product of mass and velocity of particle

m=mass of particle

v= velocity of particle

l=(6.626*10^-34)/(1.673810^-27 *2.83*10^4)

=1.399*10^-11 m