'A' Level Medical Option Questions - X-Rays
Q1. The simplified diagram shows a modern X-ray tube.
(a) For each of the labelled parts, state what it is and explain its purpose.
A is a glass tube 
It is sealed and evacuated. It allows electrons to travel unimpeded
B is a rotating anode Rotation of the anode spreads out the heated area on the target It is made of metal (tugsten or molybdenum) and emits X-rays when hit by (energetic) electrons
C is the filament [or cathode] It is the heat source necessary for the release of electrons from surface of cathode by thermionic emission
D is the lead housing It prevents X-rays from escaping in unwanted directions
(8 mark)
(b) On the diagram draw and label
(i) the direction of the electron beam,
See diagram - path of electrons shown from filament (C) to anode (B)
(ii) the direction of the useful X-ray beam.
See diagram - path of X-rays shown starting at anode (B) at the point where the electrons hit, and emerging through window in lead housing (D)
(2 marks)
(Total 10 marks)
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