Electromagnetic SpectrumCopy
Cheat Sheet: Electromagnetic Spectrum (O Level / IGCSE Physics)
1. Electromagnetic Spectrum Order
Order of Frequency (↑ Increasing)
Radio waves < Microwaves < Infrared < Visible light < Ultraviolet < X-rays < Gamma rays
Order of Wavelength (↓ Decreasing)
Radio waves > Microwaves > Infrared > Visible light > Ultraviolet > X-rays > Gamma rays
2. Speed of Electromagnetic Waves
- In vacuum:
c = 3.0 × 10⁸ m/s - In air:
Approximately same as in vacuum
3. Applications of Electromagnetic Waves
| Region | Applications |
|---|---|
| Radio waves | Radio and TV broadcasting, astronomy |
| Microwaves | Satellite TV, mobile phones, Bluetooth, microwave ovens |
| Infrared | Household appliances (e.g. toasters), remote controls, intruder alarms, thermal imaging, optical fibres |
| Visible Light | Human vision, photography |
| Ultraviolet | Security markings, detecting counterfeit notes, sterilising water |
| X-rays | Medical imaging (bones), security scanners, detecting cracks in metal, treating cancer |
| Gamma rays | Killing cancer cells, sterilising food/equipment, detecting flaws in metal structures |
4. Dangers of Electromagnetic Radiation
(a) Heating of Soft Tissues
- Caused by excessive exposure to:
- Microwaves and Infrared
- Leads to:
- Burns, heating of body tissues (especially internal organs in microwave range)
(b) Ionising Radiation Effects
- Caused by:
- Ultraviolet, X-rays, Gamma rays
- Effects:
- UV: skin cancer, cataracts
- X-rays & Gamma rays: cell mutation, cancer
- Damage to DNA and internal tissues