The Electromagnetic Spectrum

By Anna Rubinstein 10H

What is it?

The Electromagnetic Spectrum is the complete range of electromagnetic wavelengths.

E.M waves are transverse. All E.M waves travel through vacuums and space at the same speed (300 million meters per second, or 3X10^8 m/s. This is the speed that everything is set by, or the speed of light. There are no gaps in the E.M spectrum, if a wave speeds up, it will pass into a new spectrum immediately.

The Spectrum

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Radio Waves

Radio waves travels at the speed of light in a vacuum, but when they pass through objects, they slow down depending on the object's density. Radio waves are used mainly for telecommunications.


Their speed ranges from 1 meter to 1 millimeter. Uses include telecommunications, food heating appliances and radar technology.


Infrared is just by visible light, beyond red. Its wavelength is between 700 nanometers to 1 millimeter. Discovered by William Herschel the astronomer in 1800. Nowadays they are used by the military for night-vision goggles, and for thermography. IR waves are also used for heating.

Visible Light

Visible light waves are the only Electro Magnetic waves humans can see. Their wavelength is between 390 to 700 nanometers. The spectrum does not have colours like pink, because they have been made out of multiple wavelengths. Red light has the shortest wavelength, and violet has the longest.

Ultra Violet

Found in many specialized types of lights including sunlight, tanning lights and blacklights. With a wavelength of between 400 to 10 nanometers, UV waves closely follow visible light. Although UV rays are technically invisible, some children and young adults can see them under the correct conditions.


Most x-rays have a wavelength of 0.01 to 10 nanometers. They are often used by radiologists to take a picture of someone's arm, for example, and you can see from the picture if they have broken a bone. Another main use for x-rays is by airport security. Because the x-rays are reflected when they come into contact with dense substances, people use them for bomb detection.


Gamma rays are largely absorbed by the Earth's atmosphere. They can be used to change the colour of some semi-precious stones, and US security are starting to use them for cargo security. They are used to sterilize medical and scientific equipment, a process called Irradiation.