'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)