Ratio of number density of holes is `(7)/(5)` and ratio of their current is `(7)/(4)` in a semiconductor. The ratio of their drift velocity is …….

Options

A. `(4)/(7)`
B. `(5)/(8)`
C. `(4)/(5)`
D. `(5)/(4)`

Answer

D

Explanation

`(5)/(4)`
Current in semiconductor `I=nAv_(d)e`
`therefore v_(d)=(I)/(nAe)`
`therefore v_(d ) prop (I)/(n) [because "A, e constant"]`
`therefore ((v_(d))_(e))/((v_(d))_(h))=(I_(e ))/(I_(h))xx(n_(h))/(n_(e ))`
`=(7)/(4) xx (5)/(7)=(5)/(4)`