1. Across what potential difference does an electron have to be accelerated in order to reach the speed v = 9e7 m/s?

Non-relativistically V

Relativistically V

When should you use relativistic calculations?

2. An electron entering Thomson's e/m apparatus (Figure 3.2 and 3.3) has an initial velocity (in horizontal direction only) of 0.7 107 m/s. Lying around the lab is a permanent horseshoe magnet of strength 1.3 10-2 T, which you would like to use.

(a) What electric field will you need in order to produce zero deflection of the electrons as they travel through the apparatus? V/m

(b) When the magnetic field is turned off, but the same electric field remains, how large a deflection will occur if the region of nonzero E and B fields is 2 cm long?
cm

Figure 3.2

Figure 3.3

3. A photon of wavelength 2.2 nm Compton scatters from an electron at an angle of 90°. What is the modified wavelength? (Enter your answer correct to 5 significant figures.)
nm
What is the percentage change, / ?
%

4. A photon having 27 keV scatters from a free electron at rest. What is the maximum energy that the electron can obtain?
keV