Radio Waves

Radio waves are a type of electromagnetic radiation. A radio wave has much longer wavelength than does visible light. We use radio waves extensively for communications.

Radio waves have wavelengths as short as a few millimetres and as long as hundreds of kilometers. Visible light, for comparison is about 5,000 times shorter than the shortest wavelength radio waves. Radio waves oscillate at frequencies between a few kilohertz and a few terahertz. "Far infrared" radiation borders radio waves on the electromagnetic spectrum; far IR is slightly higher energy and shorter wavelength radiation than radio.

Microwaves, which we use for cooking and for communication, are short wavelength radio waves. Various frequencies of radio waves are used for television and FM and AM radio broadcasts, military communications, mobile phones, ham radio, wireless computer networks, and numerous other communications applications.

Most radio waves pass freely through Earth's atmosphere. However, some frequencies can be reflected or absorbed by the charged particles in the ionosphere.

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Infrared energy is in use all around us. Infrared techniques are of great value in many industrial applications and are considered indispensable in many others. The possibilities of its application appear to be limited only by the imagination and skill of the user.

When the waves are too long they are “seen” as infrared, when they are too short they are “seen” as ultraviolet. Shorter than the ultraviolet are X-rays and much shorter than the shortest of these are the gamma rays, and finally the cosmic rays.

The penetrative power of these increases as the wave length decreases.

To sum up: all these electromagnetic waves travel through the ether at the same enormous speed; the different effect which they produce depends entirely upon their length.

X-raying is very important in metallic welding. X-rays were discovered by Roentgen after whom they are sometimes called. The discovery of X-rays was quickly followed by their application in medicine.

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Receiver

Various types of radio receivers may include:

Consumer audio and high fidelity audio receivers and AV receivers used by home stereo listeners and audio and home theatre system enthusiasts.

Communications receivers are used as a component of a radio communication link, characterized by high stability and reliability of performance.

Simple crystal radio receivers (also known as a crystal set) which operate using the power are received from radio waves.

Satellite television receivers are applied to receive television programming from communication satellites in geosynchronous orbit.

Specialized-use receivers such as telemetry receivers allow the remote measurement and reporting of information.

Measuring receivers are calibrated laboratory-grade devices that are used to measure the signal strength of broadcasting stations, the electromagnetic interference radiation emitted by electrical products, as well as to calibrate RF attenuators and signal generators.

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