Question

An electron and a photon each has a wavelength of 1.0nm. Find (a) their momenta, (b) the energy of the photon , and © the kinetic energy electron.
Take `h=6.63xx10^(-34) Js`.
A.
B.
C.
D.

Answer 1

Correct Answer - `(i) 6.6xx10^(-25)kgms^(-1), 6.6xx10^(-25)kgms^(-1) (ii) 1.98xx10^(-16) J (iii) 2.39xx10^(-19)J`
(i) Momentum of photon. `p=h/lambda=(6.6xx10^(-34))/(1xx10^(-19))`
`=6.6xx10^(-25)kgms^(-1)`
Momentum of electron, `p=(6.6xx10^(-34))/(1xx10^(-9))`
`=6.6xx10^(-25)kgms^(-1)`
(ii) Energy of photon, `E=(hc)/lambda`
`=(6.63xx10^(-34)xx3xx10^(8))/(1xx10^(-9))=1.98xx10^(-16)J`
(iii) Kinetic energy of electron, `K=(p^(2))/(2m)`
`=((6.6xx10^(-25))^(2))/(2xx(9.1xx10^(-31)))=2.39xx10^(-19)J`