SEC G3 Combined Science Physics component K326/K327
CP10: Electromagnetic Spectrum
Compare spectrum regions, uses, and hazards through frequency and interaction.
Reviewed for the 2027 cohort on 19 July 2026. The official syllabus remains authoritative for assessable wording and paper details.
Core notes
The electromagnetic spectrum is one family of transverse waves, ordered by wavelength or frequency and distinguished in practice by how each region interacts with matter.
One spectrum and its order
Every electromagnetic wave is transverse and all travel at the same speed in vacuum. They require no material medium.
Begin at the long-wavelength, low-frequency end with radio waves, then move through microwaves, infrared, visible light, ultraviolet, and X-rays to gamma radiation at the short-wavelength, high-frequency end.
Uses across the spectrum
Radio waves support broadcasting, astronomy, and RFID. Microwaves serve mobile links, satellite television, and ovens. Infrared is used in remote controls, intruder alarms, and thermal imaging, while visible light supports photography and optical fibres.
Ultraviolet is used in sunbeds, bank-note authentication, and water disinfection. X-rays support medical imaging, security screening, and industrial defect detection. Gamma radiation is used for food sterilisation, cancer detection, and treatment.
Over-exposure hazards
High exposure can damage living cells. Lower-frequency regions can cause harmful heating. Ultraviolet can trigger photochemical damage such as sunburn and increase skin-cancer risk. X-rays and gamma rays are ionising and can damage tissue and DNA.
A useful answer links the region, interaction, exposure, and biological effect rather than saying only that radiation is dangerous.
Formulae and relationships
This chapter is assessed mainly through models, field patterns and explanations. Build the causal chain before adding any calculation.
Worked examples
Example 1: Choose a region for finding hidden defects inside a metal component and state one safety concern.
- The wave must penetrate the component.
- Industrial defect detection is a prescribed X-ray use.
- X-rays ionise matter, so exposure must be controlled.
Answer: Use X-rays with shielding and controlled exposure because they are ionising.
Chapter checkpoint
Use these three moves to organise the topic before attempting a mixed or practical question.
- Order electromagnetic regions by frequency and wavelength while keeping their vacuum speed equal.
- Link each use to a relevant transmission, absorption, penetration, heating, or detection property.
- Match heating or ionising hazards to exposure controls without treating every region as equally harmful.
Official outcome coverage
K326 CP10: 4 mapped outcomes, references CP10(a), CP10(b), CP10(c), CP10(d). Check the official K326 syllabus.
K327 CP10: 4 mapped outcomes, references CP10(a), CP10(b), CP10(c), CP10(d). Check the official K327 syllabus.
The outcome wording is not reproduced here. The relevant official syllabus remains authoritative for exact assessable scope.
Practical and data connection
Interpret detector or intensity data for electromagnetic radiation. Identify what is measured, keep distance and exposure conditions controlled, and do not claim direct sensory observation of an invisible region.
Exam traps and retrieval check
Avoid these traps
- Reversing wavelength and frequency order.
- Assigning one region a different vacuum speed.
- Naming a use without matching the correct spectrum region.
Check from memory
Which region has the longest wavelength?
Radio waves.
Name one ultraviolet use.
Bank-note authentication or water disinfection.
What makes X-rays hazardous?
Their ionising effect can damage cells.
Official Combined Science scope
This shared Combined Physics owner serves both K326 and K327. The electromagnetic spectrum, ordering, named uses, and hazards from over-exposure.