Electromagnetic radiation and spectra

The electromagnetic spectrum

In the year 1860, a Scottish physicist James Clerk Maxwell proved that light was a mixture of electromagnetic waves.

This meant that there were many more electromagnetic waves beyond infrared or ultraviolet. Soon in the early years of the 20th century, physicists had discovered or artificially produced several other types of electromagnetic waves.

This completed the electromagnetic spectrum.

The speed of electromagnetic waves

Maxwell had predicted that all electromagnetic waves will have the same speed through empty space (vacuum). This prediction came true and it has been found that all waves in the electromagnetic spectrum have the same speed in vacuum.

Electromagnetic waves travel at a speed of about 300,000,000 m/s or 3 x 108 m/s through vacuum. This is extremely close to the speed of light. Like light, the speed of electromagnetic waves depends upon the substance through which they are travelling.

Wavelength and frequency

All electromagnetic waves have different wavelengths and frequencies.

For example:

E Red light has a greater wavelength than violet light.

E Violet light has a greater frequency than red light.

Uses of electromagnetic waves


Electromagnetic wave Use
Radio waves Radio waves are used to broadcast radio signals
Microwaves Microwaves are used in satellite television broadcasting.   Microwaves are also used in transmitting mobile phone signals between masts.
Infrared waves Infrared waves are used in remote controls for controlling devices such as televisions, air conditioners, etc.   Infrared radiation is also used in grills and toasters and in burglar alarm systems.
X-Rays X-Rays are used in security scanners at airports.   X-Rays are also used in hospitals and clinics to see inside patient’s bodies.
Gamma rays Gamma rays are used in medical diagnosis and also in detecting faults in a pipeline.   Gamma rays are used in radiation therapies to treat people with cancer as well as in food irradiation and sterilisation.   More detailed information on gamma rays can be found out in our guide to radioactivity.


Electromagnetic hazards

Though electromagnetic waves have a smorgasbord of uses, they also have some hazards that need to be taken into consideration.

All types of radiation can be hazardous including bright light which can blind our eyes!

Microwaves are used to warm food in ovens; care must be taken and they must be checked in order to confirm that they don’t have any radiation leaking out of them.

Telephone engineers must take care by ensuring they aren’t exposed by too much of microwaves while working on telephone masts of a mobile phone network.

Even the people working with X-Rays must be very cautious to minimise their exposure towards X-Rays while a patient is being examined. This can be done by maintaining a long proximity with the X-Ray source.

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