My reply2:

Dear Professor Hwang

I am sorry for the long delay in replying to your mail as this was due to my preoccupation with the conduct of the laboratory examinations in my college.

1. Firstly I would like to correct my earlier assumption that the velocity of the particle initially is uniform, which should be ‘accelerating’ under the force of the electric field.

The evaluation of the motion will be governed by (Ref: Chapter on ‘Interaction of Fields and Matter’ in the book titled “ Electromagnetic Waves and Radiating Systems” by Ed. C. Jordan and Keith G. Balmain Publ: Prentice-Hall.) the following equations:

Work done by the field on the particle moving from point 1 to point 2

W = (integral) F.ds from Pt1 to Pt2 ----(1)

with F = m dv/dt

where v = velocity of the particle

and m = mass of the particle

and thus, (1) reduces after integration

W = 1/2 m (v2 squared - v1 squared) ------ (2)

where v2 = vel at point 2 and v1 = vel at point 1.

Eqn 2 states that the work done is equal to the increase in “kinetic energy”.

2. Now, if it considered that the electric field were suddenly brought to zero when the particle reached point 2, then the particle would continue to travel with velocity v2.

3. If this sequence of events were to be studied using a Cathode Ray Tube, the screen of the tube, if originally was at zero potential will acquire a (negative or positive) potential by the charge (negative or positive) on the particle after the field is switched OFF. The particle will lose its kinetic energy and produce some heat on the screen.

Please confirm whether my reasoning is correct.

Other books I referred are:

1. Fundamentals of Television Engineering by Glen Glasford Publ: Tata McGraw Hill

2. Physics by Resnick and Halliday

3. Electronic and Radio Engineering by F.E. Terman et al . Publ: Mc Graw Hill