In the “old daysâ€, televisions were made from Cathode Ray Tubeswhereby a beam of
electrons rapidly swept across the inside of the screen as a resultof strategic deflections
from magnetic fields acting on the beam. Suppose that Frank has amassive 2000 inch
TV in which the image has to be updated 100 times per second (tominimize the
appearance of “flickerâ€) and that there are 100,000 rows.
(a) Show that the electron beam moves across the screen with aspeed v  c .
(b) Explain why this superluminal speed does not contradictrelativity. In particular, why
can’t information be transmitted from one side of the screen to theother with v  c ?
