Electromagnetic Waves

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Electromagnetic Waves by Mind Map: Electromagnetic Waves

1. Electromagnetic spectrum

1.1. Gamma rays

1.1.1. Source:Cosmic rays, radioactive decay, nuclear reactions Detection:Geiger-Muller tube, photographic film Uses: Radiotherapy, Detection of cracks and faults

1.2. X-Rays

1.2.1. Source: X-ray tubes Detection: Photographic film, fluorescent screen Uses: X-ray pictures, scanning of luggages

1.3. Ultraviolet(UV) radiation

1.3.1. Source: Mercury vapour lamps, the Sun Detction: Photographic film, fluorescent screen, dye, photocell Uses: Sterilisation, detect forgery

1.4. Visible Light

1.4.1. Source: Hot bodies, the Sun Detection: The eye, photographic film, photocell Uses:telecommunications(optic fibre) , medical investigation(endoscope)

1.5. Infrared radiation

1.5.1. Source: Warm bodies, the Sun Detection: Photoconductive cell, special photographic film Uses:Remote control, Thermmography, weather forecating, night vision devices

1.6. Microwaves

1.6.1. Source: Klystron tube Detection: Valve circuit arranged as a microwave receiver Uses:Heating and cooking of food, radar, satellite and mobile communications

1.7. Radio waves

1.7.1. Source: TV and radio transmitter Detection:Aerial of TV and radio receiver Uses:TV and radio broadcast, cordless phone communication

2. Properties

2.1. They are transverse waves

2.2. They travel at 3.0 x 10 to the power of 8 m/s in vacuum.

2.3. Do not require medium for propagation

2.4. Transmit energy from one point to another

2.5. Exhibit wave properties such as reflection and refraction

2.6. When travel from a medium to another, their speed and wavelength change, but their frequency stays constant

3. An electromagnetic wave is a wave which consists of an electric field and a magnetic field vibrating perpendicularly to each other

4. Special properties and Hazards

4.1. Gamma rays and X-rays have high penetrating and ionising power. When absorbed by body, ionisation of body cells may occur, causing radiation sickness like cell mutation, cancer etc.

4.2. Fluorescent substances glow in the dark because they absorb ultraviolet radiation and re-emit visible light.

4.3. Excessive exposure to ultraviolet radiation by human being can result in pigmentation and skin cancer

4.4. Visible light consists of seven colours: red, orange, yellow, green, blue, indigo and violet. Therefore when passed into a prism, red light refracts the least while violet light refracts the most, resulting in dispersion of white light

4.5. All objects emit infrared radiation. Objects with higher temperature emit infrared radiation of higher frequency(shorter wavelength). At very high temperatures, red light is emitted and object becomes 'red hot'. Further increase cause the object to become 'white hot'.

4.6. Microwaves and radio waves transmit energy over long distances due to their long wavelengths

4.7. Radio waves are further classified into several types of waves based on wavelengths: long waves, medium waves, short waves, very high frequency waves and ultra high frequency waves