Electromagnetic waves Unit 14

1. Properties of EM Waves

1.1. No electric charge is carried through EM waves (Neither negatively nor positively charged)

1.2. No medium is required and EM wave can travel through vacuum.

1.3. 3 x 3x10^8 ms-1 in vacuum, slowing down in when travelling through different optical densities

1.4. EM Waves obey the laws of reflection and refraction.

1.5. EM Waves are transverse waves » Electric and magnetic fields that oscillate 90* to each other.

1.6. Frequency remains the same all the time Equation » v = f x λ

1.7. Transfer energy from one place to another

2. Uses of Electromagnetic Waves

2.1. Gamma Rays --> High energy » Kill cancer cells in cancerous tumours

2.2. X-rays Medical and everyday applications -->Diagnose fractures (imagery) and Airport scanners. Can penetrate through all materials other than lead.

2.3. Ultraviolet - 1) Sunbed --> Shorter frequency UVA » For artificial tanning 2) Sterilisation of medical equipment --> Longer frequency UVB/C » Germicidal lamps

2.4. Visible light: Optical fibres--> For telecommunication and medical purposes

2.5. Infrared Remote controllers and ear thermometers --> Sensors detect rise in temperature through the amount of infrared radiation present

2.6. 1) Microwaves, Oven --> Water molecules vibrate millions of times a second to create heat from friction 2) Satellites --> Can penetrate haze, light rain, snow, clouds and smoke with proper alignment

2.7. Radio waves; 1) Radio --> AM and FM radios have different wavelengths 2) Telecommunications --> Longer wavelengths » Able to go around obstructions

3. Effects of electromagnetic waves

3.1. Infrared heating --> Human skin absorbs infrared waves from BBQ pits to make humans feel warm. No permanent damage to human.

3.2. Ionisation and effects of ionising radiation on living matter --> Ionisation, the process of forming an ion, which is an electrically charged atom or molecule. 1) Molecular level -- Irritation of human tissues causing damage to proteins, nuclei acids, and other vital molecules found in cell. 2) Sub-cellular level -- Damage to DNA-containing chromosomes. 3) Organism level -- Overexposure leads to premature ageing and lifespan shortening. 4) Pregnant ladies -- Exposure of developing fetus to X-ray imagery may result in a deformed baby. Abnormal cell division and leukaemia