1. What are Electromagnetic Waves?
1.1. They consist of electric and magnetic waves which oscillate perpendicularly to each other
1.2. They are non-physical and transverse waves
2. What are their properties?
2.1. They are transverse waves
2.2. They do not need a medium to propagate
2.3. They travel at a constant speed of 3 X 10^8 ms^1
2.4. They obey the laws of reflection and refraction
2.5. They obey the general wave equation .
2.5.1. Speed of Wave= Frequency X Wavelength
3. Electromagnetic Spectrum
3.1. Consists of Electromagnetic Waves of a continuous range of frequencies.
3.1.1. Gamma Ray
3.1.1.1. Emitted during radioactive decay of unstable atoms and during Nuclear reactions
3.1.1.1.1. Helps to kill cancerous tumours and cells. Also able to kill harmful bacteria viruses.
3.1.1.1.2. Sterilise medical instruments
3.1.2. X-Ray
3.1.2.1. Found in X-ray tubes
3.1.2.1.1. Used in X-ray test to detect damages to the bone.
3.1.2.1.2. Also used in scanners at aiports for secuirty.
3.1.3. UltraViolet Ray
3.1.3.1. From Sunlight.
3.1.3.1.1. Produces Suntan
3.1.3.1.2. Kills Bacteria
3.1.3.1.3. Check for counterfeit notes
3.1.4. Visible Light
3.1.4.1. Emitted from Sun, or heated bodies.
3.1.4.1.1. Used in optical fibres, light photography and endoscopy.
3.1.5. InfraRed
3.1.5.1. Emitted by hot objects
3.1.5.1.1. Used in remote control of household devices like the television
3.1.5.1.2. Also used in Night Vision equipment and Thermal Imaging cameras.
3.1.6. Micro Waves
3.1.6.1. Produced in special electronic devices eg. klystron.
3.1.6.1.1. Used to heat up food by transferring energy to water molecules in the food causing a heating effect.
3.1.6.1.2. Used in satellite communication.
3.1.7. Radio
3.1.7.1. Produced by electrons oscillating in electric circuits.
3.1.7.1.1. Used for tv and radio transmissions
3.2. The higher the frequency, the lower the wavelength,or vice versa. Also, the higher the frequency, the greater the amount of energy carried by the wave.
4. Harmful Effects
4.1. Absorbing Electromagnetic Waves of higher frequencies(eg X-rays and Gamma Rays)
4.1.1. Ionisation of cells and tissues
4.1.1.1. Ionisation knocks off electrons from atoms, forming ions and free radicals which can cause damage to cells and tissues
4.2. Absorbing Electromagnetic Waves of lower frequencies(eg Light, Infrared and Microwaves)
4.2.1. Heating effect of cells and tissues