The electron beam inside an old television picture tube is 0.40 mm in diameter and carries a current of 50 μ_A. This electron beam impinges on the inside of the picture tube screen.
a. How many electrons strike the screen each second?
b. What is the current density in the electron beam?
c. The electrons move with a velocity of 4.0 × 10⁷ m/s. What electric field strength is needed to accelerate electrons from rest to this velocity in a distance of 5.0 mm?
d. Each electron transfers its kinetic energy to the picture tube screen upon impact. What is the power delivered to the screen by the electron beam?