The Electromagnetic Spectrum by year 12 physics students

Radio Waves

Nicholas Savva 12I

Radio waves are a part of the electromagnetic wave spectrum with frequencies of between 3 KHz and 300 GHz, and wavelengths of between 1mm and 1km.

Like all the electromagnetic waves it has the same speed in a vacuum of 3 x E8 ms^-1

The frequency range of radio waves is split up into 4 categories:

· Long wave (1-2km in wavelength. The radio station “Atlantic 252” broadcasts here

· Medium Wave (100m in wavelength) Used for AM radio stations such as BBC Radio .

· Very High Frequency (VHF) (around 2m in wavelength) FM radio stations are broadcast on these frequencies such as BBC Radio 1. Further up the VHF band are used by civilian aircraft and taxis.

· Ultra High frequency (UHF) (less than 1m in wavelength) used for Police radio, TV, and military communications

The diagram below illustrates this:


Radio waves are typically transmitted from a transmitter, which creates the wave, and received from an antenna. Radio waves travel better through some materials better than others. For example, the lower atmosphere of the earth allows waves to travel easily, whereas the uppermost layers of the earth’s atmosphere (the ionosphere) contains high energy, ionized radiation from the sun which prevents the waves travelling . This means the waves are reflected, but this is not necessarily a bad thing, as it allows the waves to stay inside the earth, rather than passing through the atmosphere and going off into space.

The picture below left shows a rough plot of Earth’s atmospheric transmittance (or opacity) to various wavelengths of radio waves.

image     image

The ionosphere is a region of the upper atmosphere, from about 85 km to 600 km altitude, and includes the thermosphere and parts of the mesosphere and exosphere. It is distinguished because it is ionized by solar radiation.


Radio waves were first predicted by mathematical work done in 1867 by Scottish mathematical physicist James Clerk Maxwell. Maxwell noticed wavelike properties of light and similarities in electrical and magnetic observations. He then proposed equations that described light waves and radio waves as waves of electromagnetism that travel in space, radiated by a charged particle as it undergoes acceleration. In 1887, Heinrich Hertz demonstrated the reality of Maxwell’s electromagnetic waves by experimentally generating radio waves in his laboratory. He showed how varying an electrical current could be projected into space as radio waves. Guglielmo Marconi, an Italian inventor sent and received the first radio signal in 1895.


Guglielmo Marconi, 1st Marquis of Marconi (25 April 1874 – 20 July 1937) was an Italian inventor and electrical engineer, known for his pioneering work on long distance radio transmission.

In addition to Marconi Nikola Tesla is credited with being the first person to patent radio technology; the Supreme Court overturned Marconi’s patent in 1943 in favour of Tesla.

Nikola Tesla (10 July 1856 – 7 January 1943) was a Serbian American inventor, electrical engineer, mechanical engineer, physicist, and futurist best known for his contributions to the design of the modern alternating current (AC) electricity supply system.


Usage of radio waves has evolved through the 20th century as FM radio became publically usable in 1933.

The main use of radio is to convey information from one place to another through different media such as air, space and non-conducting materials without wires. Besides being used for transmitting sound and television signals, radio is used for the transmission of data in coded form. In the form of radar it is used also for sending out signals and picking up their reflections from objects in their path. Long-range radio signals enable astronauts to communicate and carry information from space probes as they travel to distant planets. For navigation of ships and aircraft the radio range, radio compass (or direction finder), and radio time signals are widely used. Radio signals sent from global positioning satellites can also be used by special receivers for a precise indication of position. Digital radio, both satellite and terrestrial provide improved audio clarity and volume. Various remote-control devices, including rocket and artificial satellite operations systems and automatic valves in pipelines, are activated by radio signals. The development of the transistor and other microelectronic devices led to the development of portable transmitters and receivers. Mobile and cordless telephones are actually radio transceivers. Many telephone calls routinely are relayed by radio rather than by wires; some are sent via radio to relay satellites. Some celestial bodies and interstellar gases emit relatively strong radio waves that are observed with radio telescopes composed of very sensitive receivers and large directional antennas.

Socially radio waves are an everyday part of our lives, as we use them for many things including, mobile phones, television, Wifi/3G/4G internet, radio, even garage door openers. Because of this, communication in this day and age is easier and quicker than it has ever been. This is undoubtedly an advantage to humanity, but there has been dispute over whether having radio waves around us is a health risk. Mobile phones are said to pose the most risk as they emit a small amount of electromagnetic radiation (since they are emitting radio waves with radio-frequency energy), and because we usually hold phones on our head, there is a chance that some of this radiation is absorbed by our human tissue. Various studies claim that mobile phone usage is linked to cancer, where as other studies report that there is no connection between mobile phone usage and cancer. Officially, it is stated that mobile phones do not cause any health problems, but the research continues.

2 thoughts on “The Electromagnetic Spectrum by year 12 physics students

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