State two uses of ultraviolet radiation and, for each use, explain why ultraviolet radiation is suitable for that purpose.

Cambridge International IGCSE Physics (0625) — 3.3 Electromagnetic spectrum · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Use 1: sterilisation of water and surfaces
Explanation: UV‑C radiation has enough energy to break the bonds in the DNA of microorganisms, preventing replication and killing them.
Use 2: detecting forged banknotes
Explanation: UV light causes certain inks used on genuine notes to fluoresce, making forgeries, which lack the ink, easily visible.

Examiner tips

State a use and give a clear, concise explanation linked to UV energy or fluorescence.
Use correct terminology: UV‑C, DNA damage, fluorescence, inks.
Keep each point brief – 2 marks each.

Common mistakes

Mixing up UV‑A with UV‑C – only UV‑C is effective for sterilisation.
Failing to link the use to a specific property of UV radiation.

Mark scheme (4 marks)

Use 1: sterilisation of water/surfaces / detecting forged banknotes / fluorescent lamps / sunbeds / checking for cracks in metals (any one correct use)
Explanation for use 1: linked correctly to a property of ultraviolet radiation, e.g. ultraviolet causes fluorescence / has sufficient energy to kill microorganisms / causes certain materials to glow / damages DNA of bacteria
Use 2: a different correct use of ultraviolet radiation (any one from the list above, different from use 1)
Explanation for use 2: correctly linked to a property of ultraviolet radiation relevant to the stated second use

Key terms in this question

ultraviolet radiation