A photographer notices that some materials appear a different colour when viewed under ultraviolet (UV) light compared to visible light. Explain why ultraviolet radiation and visible light behave differently when interacting with these materials, and state one property that ultraviolet radiation and visible light share as members of the electromagnetic spectrum.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Ultraviolet radiation and visible light are both parts of the electromagnetic spectrum, but they have different frequencies and wavelengths.
Model answer (4 marks)
Ultraviolet radiation has a higher frequency than visible light.
Because the frequency is higher, each UV photon carries more energy, so it can excite electrons in the material to higher energy levels or break bonds, producing different colours or fluorescence.
Both UV and visible light travel at the same speed in a vacuum (and in air) and are transverse electromagnetic waves.
Because the frequency is higher, each UV photon carries more energy, so it can excite electrons in the material to higher energy levels or break bonds, producing different colours or fluorescence.
Both UV and visible light travel at the same speed in a vacuum (and in air) and are transverse electromagnetic waves.
Examiner tips
- Mention higher frequency → higher energy to justify colour change; state shared property explicitly; keep answer concise to fit 4 marks
Common mistakes
- Confusing wavelength with frequency; saying UV has longer wavelength; omitting the shared property of speed or wave type
Mark scheme (4 marks)
- Ultraviolet radiation has a higher frequency than visible light
- Higher frequency means higher energy (per photon / wave), so UV interacts differently with materials
- Both UV and visible light travel at the same speed in a vacuum / through air
- Both UV and visible light are transverse waves (accept: both do not need a medium / can travel through a vacuum)
Key terms in this question
electromagnetic spectrum · ultraviolet radiation · visible light
Related
- All OCR GCSE Physics A: Gateway Science (J249) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →