Parts of the electromagnetic spectrum
Source, detection and application
- Electromagnetic waves carry energy. The waves consist of transverse vibrations in electrical and magnetic fields, not vibrating particles.
- Electromagnetic waves do not need matter to travel through - they can travel through empty space (a vacuum).
- In a vacuum, all electromagnetic waves travel at \(3 \times 10^{8}m\,s^{-1}\) - the fastest speed possible.
- When electromagnetic waves travel through matter (for example, light passing through air or glass), they travel a bit slower than this but rarely less than half as fast as in a vacuum. The value for light travelling through a glass A fine glass fibre, through which light travels by total internal reflection, from one end to the other., for example, is taken as \(2 \times 10^{8}m\,s^{-1}\).
The table below demonstrates the electromagnetic spectrum.
| Type of wave | Typical source | Example of detector | Approximate wavelength | Typical users | Dangers of over exposure |
| Radio: LW, MW and VHF | electronic circuits | aerial | 1km, 100m and 1m | communications, radio, TV | safe (unless very concentrated) |
| Microwaves | electronic circuits | aerial | 1cm \((10 ^{-2}m)\) | communications satellites, telephony, heating water and food | burning, if concentrated |
| Infra red (IR) | electronic devices, warm objects, sun | electronic detectors, heat-sensitive papers, black-bulb thermometer | 0.1mm \((10 ^{-4}m)\) | detector in security lighting, remote controls (e.g. TV) | burning, if concentrated |
| Light; Red, Orange, Yellow, Green, Blue, Indigo, Violet | electronic devices (eg LED), sun | eye, photographic film, electronic components (eg LDR) | 0.001mm \((10 ^{-6}m)\) | seeing, photography, communication (eg in optical fibres), laser surgery | burning, blindness if concentrated |
| Ultraviolet (UV) | sun, gas discharge, lamps | causes fluorescence (glowing) in some objects, film | 0.00001mm \((10 ^{-8}m)\) | sun-tan lamp, making ions, making vitamin D, killing bacteria in water treatment plants | sunburn, skin cancer, retinal damage |
| X-rays | very fast electrons hitting a metal target | photographic film | \(10^{-10}m\) | imaging breaks/defects in bones, hidden devices | cell destruction, cell mutation, cancer |
| Gamma rays (\(\gamma\)) | radioactive nuclei decaying | photographic film, GM tube | \(10^{-12}m\) | medical tracers, killing cancerous cells, sterilisation of surgical equipment | cell destruction, cell mutation, cancer |
| Type of wave | Radio: LW, MW and VHF |
|---|---|
| Typical source | electronic circuits |
| Example of detector | aerial |
| Approximate wavelength | 1km, 100m and 1m |
| Typical users | communications, radio, TV |
| Dangers of over exposure | safe (unless very concentrated) |
| Type of wave | Microwaves |
|---|---|
| Typical source | electronic circuits |
| Example of detector | aerial |
| Approximate wavelength | 1cm \((10 ^{-2}m)\) |
| Typical users | communications satellites, telephony, heating water and food |
| Dangers of over exposure | burning, if concentrated |
| Type of wave | Infra red (IR) |
|---|---|
| Typical source | electronic devices, warm objects, sun |
| Example of detector | electronic detectors, heat-sensitive papers, black-bulb thermometer |
| Approximate wavelength | 0.1mm \((10 ^{-4}m)\) |
| Typical users | detector in security lighting, remote controls (e.g. TV) |
| Dangers of over exposure | burning, if concentrated |
| Type of wave | Light; Red, Orange, Yellow, Green, Blue, Indigo, Violet |
|---|---|
| Typical source | electronic devices (eg LED), sun |
| Example of detector | eye, photographic film, electronic components (eg LDR) |
| Approximate wavelength | 0.001mm \((10 ^{-6}m)\) |
| Typical users | seeing, photography, communication (eg in optical fibres), laser surgery |
| Dangers of over exposure | burning, blindness if concentrated |
| Type of wave | Ultraviolet (UV) |
|---|---|
| Typical source | sun, gas discharge, lamps |
| Example of detector | causes fluorescence (glowing) in some objects, film |
| Approximate wavelength | 0.00001mm \((10 ^{-8}m)\) |
| Typical users | sun-tan lamp, making ions, making vitamin D, killing bacteria in water treatment plants |
| Dangers of over exposure | sunburn, skin cancer, retinal damage |
| Type of wave | X-rays |
|---|---|
| Typical source | very fast electrons hitting a metal target |
| Example of detector | photographic film |
| Approximate wavelength | \(10^{-10}m\) |
| Typical users | imaging breaks/defects in bones, hidden devices |
| Dangers of over exposure | cell destruction, cell mutation, cancer |
| Type of wave | Gamma rays (\(\gamma\)) |
|---|---|
| Typical source | radioactive nuclei decaying |
| Example of detector | photographic film, GM tube |
| Approximate wavelength | \(10^{-12}m\) |
| Typical users | medical tracers, killing cancerous cells, sterilisation of surgical equipment |
| Dangers of over exposure | cell destruction, cell mutation, cancer |
Chart showing types of electromagnetic waves
The electromagnetic spectrum ranges from long wavelength, low frequency waves (like radio waves which can be used for communication) to short wavelength, high frequency waves (like The shortest wavelength and highest energy part of the EM spectrum. Produced by radioactive materials. which can be used for medical treatment).
In the electromagnetic spectrum, waves with higher frequency have greater energy than lower frequency waves.
