The diagram shows the basic setup for the production of X-rays. A1 and A2 are two ammeters, reading 2.55 A and 2.566 A respectively. F is a filament which is also the cathode. The potential difference applied between P and Q is 50 000 V. Assume that all X-ray photons have the maximum possible energy and that one X-ray photon is emitted for every 100 electrons incident on the target. You may assume that the kinetic energy of the other electrons reappear as heat in the tube.
The rate at which heat is produced in the X-ray tube is approximately
(a) 10 W
(b) 40 W
(c) 200 W
(d) 800 W
