Join / Login
Question

A diverging electron beam enters a region of varying potentials. Intersection of equispaced equipotential plane surfaces with the plane of the paper are shown, with their potentials mentioned in the figure. If before entering this region, x and y components of the velocity of electrons are and , respectively, where m is the mass of an electron and is the electronic charge, then :

expand
This question has multiple correct options
A

the electron beam is converged

B

the electron beam is diverged

C

the electric field is uniform and is directed towards negative x-axis

D

the electric field is uniform and is directed towards positive x-axis

Hard

Solution

verified
Verified by Toppr
Correct option is
A

the electron beam is converged

C

the electric field is uniform and is directed towards negative x-axis

When an electron moves in a region of changing potential, the force acting on it at any point in its path is perpendicular to the equipotential surface at that point. This is because the rate of change of potential (or electric field strength) is greater in this direction. In other words the electron experiences a pull trying to move it perpendicular to the equipotential surfaces in the direction of increasing positive potential.
Hence , increases while is constant . 
Hence , decreases , making the electron beam convergent . 
The electric field is directed from a region of higher potential to a region of lower potential and hence it is directed towards the negative x axis.

expand

Was this answer helpful?

upvote 0
downvote0