A potential barrier of 0.5 V exists across a p-n junction
(i) If the depletion region is `5 xx 10^(7) m` wide. What is the intensity of the electric field in this region ?
(ii) An electron with speed `5 xx 10^(5) m//s` approaches the p-n junction from 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)Vm^(-1)`
(b)Suppose the electron has a speed `v_(1)`when it enters the depletion layer and `v_(2)`when it comes out of it .As the potential energy incteases by `exx0.50V,
form the principle of conservation of energy,
`1/2 mv_(1)^(2)=exx0.50+1/2 mv_(2)^(2)`
or,`1/2xx(9.1xx10^(31)kg)xx(5.0xx10^(5)ms^(-2))^(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)ms^(-1).`
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