An electron enters the region between the plates of a parallel plate capacitor at an angle `theta` to the plates. The plate width is `l`, the plate separation is `d`. The electron follows the path shown just missing the upper plate. Neglect gravity. Then,
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Options

A. `tantheta=2d/l`
B. `tantheta=4d/l`
C. `tantheta=8d/l`
D. The data given is insufficient to find a relation between d, l and `theta`

Answer

B

Explanation

Horizontal range,
`R=(2u_x xxu_y)/g=l`…….i
Maximum height `H=u_y^2/(2g)=d`……..ii
Dividing eqn ii by eqn i we have
`1/4(u_y/u_x)=d/l`
or `u_y/u_x=(usintheta)/(ucostheta)`
`=tantheta=(4d)/l`