If an electron enters a space between the plates of a parallel plate capacitor at an angle `theta_(1)` with the plates and leaves at an angle `theta_(2)` to the plates, the ratio of its kinetic energy while entering the capacitor to that while leaving will be

Options

A. `(cos^(2)theta_(2))/(cos^(2)theta_(1))`
B. `(cos^(2)theta_(1))/(cos^(2)theta_(2))`
C. `(sin^(2)theta_(2))/(sin^(2)theta_(1))`
D. `(sin^(2)theta_(1))/(sin^(2)theta_(2))`

Explanation

If `V_(1)` and `V_(2)` be the speeds of electron while entering the capacitor and while leaving it, then
`v_(1)costheta_(1)=v_(2)costheta_(2)rArr(v_(1))/(v_(2))=(costheta_(2))/(costheta_(1))`
`((K.E.))/((K.E.)_(2))=((costheta_(2))/(costheta_(1)))^(2)`