Question

n electron in a television picture tube has a classical kinetic energy of 70 keV, which is the kinetic energy that Newton would calculate using the measured speed and rest mass of the electron. What is the actual kinetic energy of the electron; that is, what is the value found using the relativistic result for the kinetic energy? (Give your answer in units of keV; don't type in a unit explicitly.)

Answer 1

Electron energy = 70 Kev ( as per Newtonian Mechanics) =    -------------------- (1)

Relativistic Kinetic energy =    where -------------------- (2)

from (1)   

E = 70 Kev = 70 X 10 ^ 3 X 1.60 x 10 ^ (-19) j = 112 x 10 ^ (-16) J

  = 15.68 X 10 ^ 7 m/s

E = m =