Electromagnetic radiation occurs all around us and throughout space. It is produced through the interaction of electric and magnetic fields. These two fields always exist together. Electromagnetic waves can have a large range of frequencies or wavelengths.
They are seven types of electromagnetic spectrum. They are: * Radio waves e.g used in TV and radio transmissions * Microwaves e.g used for mobile phone links * Infrared waves e.g used for some alarm systems * Visible light e.g used by humans and most animals to receive information about their surroundings * Ultraviolet e.g used in tanning beds * X-rays e.g used in radio therapy * Gamma rays e.g used to kill and/or treat certain types of cancers, detect brain and heart abnormalities.
All these waves have a number of properties in common: * They all travel at the same speed in a vacuum * They are all transverse waves. * They all consists of an oscillating electric and magnetic field
Electromagnetic waves with large wavelengths (300m) are called radio waves and are received by radios. These waves cannot diffract past a large object such as a hill
, so a house in a valley would not receive the signal from a transmitter on the other side of the hill. Their frequencies are around 100Hz. They are produced by existed electrons when they return to their normal state. Radio waves can be made to carry information by varying a combination of the amplitude, frequency and phase of the wave within a frequency band.
Electromagnetic waves with wavelengths ( 0.01m) are called microwaves and they are used for mobile phones and communications via satellite. They also do not diffract obstacles because of their short wave length. They are made in transmitters. Their frequencies are around 10 power of 10 Hz.
Infrared Waves have frequency of 10 powers of 13 Hz and their wavelengths are 10 powers of -5 m. They are used by some alarm systems. Warm bodies emit infrared waves. They can be detected by sensors, which can then activate an alarm system. It’s also used in wireless remote control.
This is a very narrow band of frequencies of band of frequencies of Electromagnetic waves that is used by humans. They receive information about their surroundings.
Within the narrow band of visible light, the different frequencies are perceived by people as different colours. The lowest frequencies of visible light, next to the infrared perceived as the colour red. The highest frequencies are perceived as violet.
Ultraviolet radiation is a band of electromagnet waves