- Home
- Standard 12
- Physics
2. Electric Potential and Capacitance
hard
An electron with kinetic energy $K _{1}$ enters between parallel plates of a capacitor at an angle $'\alpha'$ with the plates. It leaves the plates at angle $' \beta '$ with kinetic energy $K _{2}$. Then the ratio of kinetic energies $K _{1}: K _{2}$ will be ....... .
A
$\frac{\sin ^{2} \beta}{\cos ^{2} \alpha}$
B
$\frac{\cos ^{2} \beta}{\cos ^{2} \alpha}$
C
$\frac{\cos \beta}{\cos \alpha}$
D
$\frac{\cos \beta}{\sin \alpha}$
(JEE MAIN-2021)
Solution
velocity along the plate will not change.
$\therefore v _{1} \cos \alpha= v _{2} \cos \beta$
$\frac{ K _{1}}{ K _{2}} \Rightarrow \frac{ v _{1}^{2}}{ v _{2}^{2}}=\frac{\cos ^{2} \beta}{\cos ^{2} \alpha}$
Standard 12
Physics
