Electromagnetic Spectrum
Section: Physics | Syllabus: Cambridge IGCSE Combined Science (0653)
Properties of Electromagnetic Waves
- Electromagnetic (EM) waves are transverse waves - oscillating electric and magnetic fields, perpendicular to each other and to the direction of travel
- All electromagnetic waves travel at the same high speed in a vacuum: c = 3.0 × 10^8 m/s, and approximately the same speed in air
- EM waves do not need a medium - they can travel through the vacuum of space
- Like all waves, they obey the wave equation c = flambda
An electromagnetic wave: perpendicular electric and magnetic field oscillations
The Electromagnetic Spectrum
The electromagnetic spectrum is the complete range of electromagnetic waves. It is divided into seven main regions:
The electromagnetic spectrum
- In order of increasing frequency (and equivalently, decreasing wavelength): radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays
- Radio waves have the lowest frequency and longest wavelength; gamma rays have the highest frequency and shortest wavelength
| Region | Approximate Wavelength | Approximate Frequency |
|---|---|---|
| Radio waves | > 0.1 m | < 3 × 10^9 Hz |
| Microwaves | 1 mm - 0.1 m | 3 × 10^9 - 3 × 10^11 Hz |
| Infrared | 700 nm - 1 mm | 3 × 10^11 - 4 × 10^14 Hz |
| Visible light | 400 - 700 nm | 4 × 10^14 - 7.5 × 10^14 Hz |
| Ultraviolet | 10 - 400 nm | 7.5 × 10^14 - 3 × 10^16 Hz |
| X-rays | 0.01 - 10 nm | 3 × 10^16 - 3 × 10^19 Hz |
| Gamma rays | < 0.01 nm | > 3 × 10^19 Hz |
Uses of Electromagnetic Waves
Radio Waves
- Radio and television transmissions
- Radar
Microwaves
- Satellite television
- Mobile phones (cell phones)
- Microwave ovens
Infrared
- Remote controllers for televisions
- Thermal imaging
Visible Light
- Vision
- Photography
Ultraviolet
- Detecting fake bank notes
X-rays
- Medical scanning
- Security scanners
Gamma Rays
- Detection of cancer and its treatment
Harmful Effects of Electromagnetic Radiation
Excessive exposure to some regions of the electromagnetic spectrum is harmful:
- Ultraviolet: damage to surface cells and eyes, leading to skin cancer and eye conditions
- X-rays and gamma rays: mutation or damage to cells in the body
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