Electromagnetic spectrum

Explore electromagnetic waves for G2 Science Physics, from spectrum order and common properties to applications and hazards.

SEC G2 Science Physics component 2027
2 lessons

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Before you begin

Radio waves, light and X-rays look nothing alike, yet they are the same kind of wave with different wavelengths. The lessons start with what all electromagnetic waves have in common and the order of the regions of the spectrum. They then explain the uses of each region and how over-exposure can harm living cells by heating or ionising them.

Be comfortable with: wave quantities and wave speed, because v = fλ links each region’s wavelength to its frequency.

Learning goals

State that all electromagnetic waves are transverse
State that all electromagnetic waves travel at the same speed in vacuum
Order the seven electromagnetic-spectrum regions
Relate spectrum order to wavelength and frequency
State typical uses of radio waves
State typical uses of microwaves
State typical uses of infrared
State typical uses of visible light
State typical uses of ultraviolet
State typical uses of X-rays
State typical uses of gamma rays
Describe hazardous heating effects of electromagnetic over-exposure
Describe hazardous ionising effects on living cells and tissue

Syllabus statements covered

state that all electromagnetic waves are transverse waves that travel with the same speed in vacuum
describe the main regions of the electromagnetic spectrum in order of wavelength and frequency
state examples of typical uses of the following regions of the electromagnetic spectrum: (i) radio waves (e.g. radio and television communication, astronomy and RFID tags) (ii) microwaves (e.g. mobile (cell) phones, microwave oven and satellite television) (iii) infrared (e.g. infrared remote controllers, intruder alarms and thermal imaging) (iv) visible light (e.g. photography, optical fibres in medicine and telecommunications) (v) ultraviolet (e.g. sunbeds, bank note authentication and disinfecting water) (vi) X-rays (e.g. medical radiology, security screening and industrial defect detection) (vii) gamma (γ) rays (e.g. sterilising food, detection of cancer and its treatment)
describe how over-exposure to electromagnetic waves can have hazardous effects (e.g. heating and ionising effects of radiation) on living cells and tissue

Lessons

Work through them in order.

Practise and check

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Topic reference

Quick reference

Region	Typical uses
radio waves	radio and television communication, astronomy, RFID tags
microwaves	mobile phones, microwave ovens, satellite television
infrared	remote controllers, intruder alarms, thermal imaging
visible light	photography, optical fibres in medicine and telecommunications
ultraviolet	sunbeds, checking bank notes, disinfecting water
X-rays	medical radiology, security screening, finding defects in materials
gamma rays	sterilising food, detecting and treating cancer

From radio waves to gamma rays, the wavelength decreases and the frequency increases. All travel at 3.0 × 10⁸ m/s in a vacuum.

Core knowledge to remember

All electromagnetic waves are transverse waves that travel with the same speed in a vacuum.
In order of increasing frequency, the main regions are radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.
Over-exposure to electromagnetic waves can harm living cells and tissue: microwaves and infrared can heat tissue, and ultraviolet, X-rays and gamma rays can ionise and damage cells.

Common mistakes

Saying higher-frequency waves travel faster. All electromagnetic waves have the same speed in a vacuum.
Getting the order of the spectrum the wrong way round, or mixing up wavelength and frequency.
Calling electromagnetic waves longitudinal.
Saying any exposure to radiation is dangerous. The harm depends on the region, the intensity and how long the exposure lasts.