An electron passes between two parallel plate of a capacitor as shown in the diagram. The electron enters the plate at t=0 and it comes out of the plates at time t=T. The electron hits the screen at A, as shown. Now a time varying potential difference V is applied between the plates, as shown in the graph. (Neglect the gravity). The point where the electron now will strike (as compared to point A) will be

Options

A. Deflected up
B. Deflected down
C. Deflected up then down
D. Deflected down then up

Answer

A

Explanation

A positive potential on the upper plate attracts the electron and hence deflects it upwards since electric field between the plates is always downward i.e. force on electron is always upward i.e. force of electron is always upward). It would only be deflected downwards by a negative potential on the top plate.