A potential barrier of 0.50V exists across a p-n junction.(a) If the depletion region is `5.0xx10^(-7)`m wide,what is the intensity of the electric field in this region?(b) An electron with speed`5.0xx10^(5)m s^(-1)`approaches the p-n junction form the n-side.With what speed will it enter the p-side?

Explanation

(a). The electric field is `E= V//d`
`=(0.50V)/(5.0xx10^(-7)m)=1.0xx10^(6) V//m`
(b). Suppose the electron has a speed `v_(1)` when it enters the depletion layer and `v_(2)` when it comes out of it (figure). As the potential energy increases by `e xx0.50V_(1)` from the principle of conservation of energy.
`(1)/(2)mv_(1)^(2)= e xx0.50V+(1)/(2)mv_(2)^(2)`
or `(1)/(2)xx(9.1xx10^(-31)kg)xx(5.0xx10^(5) m//s^(2)=1.6xx10^(-19)xx0.5J+(1)/(2)(9.1xx10^(-31)kg)v_(2)^(2)`
or `1.13xx10^(-19)J=0.8xx10^(-19)J+(4.55xx10^(-31)kg)v_(2)^(2)`
Solving this `v_(2)=2.7xx10^(5) m//s`