Question

The wavelength of a photon having energy equal to rest energy of an electron is

Answer 1

Energy of electron at stable state= E= mC²

the momentum of photon by the debrogli equation is;
P = h/λ
p = h/ hc/e 
p= E/c
p= mC²/C
p= mC

so,
p = 9.1 x 10⁻³¹ x 3 x 10⁸
p = 27.3 x 10⁻²³ kgm/s