Part A The electron gun in an old TV picture tube accelerates electrons between
ID: 3281252 • Letter: P
Question
Part A The electron gun in an old TV picture tube accelerates electrons between two parallel plates 1.3 em apart with a 30 kV potential diference between them. The electrons enter through a small hole in the negative plate, accelerate, then exit through a small hole in the positive plate. Assume that the holes are small enough not to affect the electric field or potential. What is the electric feld strength between the plates? Express your answer to two significant figures and include the appropriate units. EValue Units Submit My Answers Give Up Part B With what speed does an electron exit the electron gun if its entry speed is close to zero? Note: The exit speed is so fast that we really need to use the theory of relativity to compute an accurate value. Your answer to part B is in the right range but a little too big Express your answer to two significant figures and include the appropriate units. ue Units Submit My Answers Give UpExplanation / Answer
a) Electric field, E = (30000)/(0.013) = 2.307 x 106 V/m
b) The energy gained in going from the negative to the positive plate is,
K = vq = 30000 x 1.6 x 10-19 = 4.8 x 10-15 J
The rest mass of an electron is m = 9.11 x 10-31 kg
K = 1/2mv2 = 4.8 x 10-15 J
0.5 x 9.1 x 10-31 x v2= 4.8 x 10-15 J
v = 1.027 x 108 m/s
Please rate my answer if you find it helpful, good luck...