Properties common to all electromagnetic waves, the full spectrum from gamma to radio waves ordered by frequency and wavelength, sources and uses of each type, and associated hazards.
All electromagnetic (EM) waves share the same fundamental properties:
EM waves differ in frequency (and therefore wavelength). The spectrum is continuous, there are no sharp boundaries between the named regions.
Higher frequency corresponds to shorter wavelength and higher energy per photon.
| Type | Typical wavelength | Typical frequency | Source | Uses | Hazards |
|---|---|---|---|---|---|
| Gamma () | m | Hz | Radioactive nuclei | Cancer treatment, sterilising medical instruments, food irradiation | Ionising, causes cancer, cell damage, genetic mutation |
| X-rays | to m | to Hz | High-voltage X-ray tubes | Medical imaging of bones, airport security scanners | Ionising, excess exposure damages cells |
| Ultraviolet (UV) | to m | to Hz | Sun, UV lamps | Detecting forged banknotes, tanning, sterilisation | Causes sunburn, cataracts, skin cancer |
| Visible light | to m | to Hz | Luminous objects, the Sun | Sight, photography, optical fibres | Generally safe at normal intensities |
| Infrared (IR) | to m | to Hz | All warm objects, heat lamps | Remote controls, thermal imaging, cooking (microwave ovens use adjacent range), solar heaters | Skin burns at high intensities |
| Microwaves | to m | to Hz | Microwave generators | Cooking, satellite communication, mobile phone networks, radar | Internal heating of body tissue |
| Radio waves | m to m | to Hz | Radio transmitters, oscillating currents | Radio and TV broadcasting, long-range communication | Generally safe |
Memory aid for order (high frequency to low):
Gamma, X-ray, Ultraviolet, Visible, Infrared, Microwave, Radio
"Gorillas eXcel Under Very Icy Mountain Ranges"
Visible light occupies wavelengths of approximately m to m.
A rattlesnake can detect EM radiation of frequency Hz. Calculate its wavelength.
Since m is just beyond the red end of the visible range ( m), this radiation is infrared, consistent with heat sensing in pit vipers.
The order of the spectrum must be memorised. Know that gamma rays have the highest frequency and shortest wavelength; radio waves have the lowest frequency and longest wavelength.
When asked which region is most dangerous, the answer depends on context: gamma and X-rays are ionising and most hazardous for cell damage. UV causes skin cancer and sunburn. Infrared and microwaves can burn tissue but are non-ionising.
For wavelength calculations: use with m s⁻¹. Always check your answer, visible light wavelengths are in the range m, so a calculation giving a very different order of magnitude signals an error.