All the wavelengths, including those we can and cannot see, make up the electromagnetic spectrum, including the entire range of electromagnetic wave frequencies.  Electromagnetic waves are made by vibrating electric charges and can travel through space.  The frequency of electromagnetic waves is the number of vibrations per second.  All of these types of waves can be reflected, refracted, and diffracted.

Radio waves have long wavelengths, emitting low-frequency waves with wavelengths of about 1-10 cm.  They are used to transmit information on the radio, television, and even phones.  In addition, they can determine the position of objects when the waves are transmitted toward an object using radar.  The location of an object can be found by measuring the amount of time it takes for a wave to bounce off an object and return.

On the electromagnetic spectrum, infrared waves have longer wavelengths than visible light but shorter wavelengths than radio waves.  As a result, much of today’s technology incorporates infrared waves used in equipment.  Examples are weather satellites that use infrared detectors to form images for meteorology or night vision equipment that detects infrared radiation and can produce images based on temperature for the military.  Infrared is also used in communication devices, such as remote controls, by emitting a narrow beam of infrared radiation to control appliances.

Visible light is the range of electromagnetic waves you can detect with your eyes.  The human eye can only see certain wavelengths, the longest red, and the shortest violet.  Red, orange, yellow, green, blue, indigo, and violet are different colors that each have different wavelengths.

Ultraviolet waves have frequencies slightly higher than visible light and can enter the skin.  They can cause sunburn and even skin cancer. On the other hand, they produce vitamin D, which is good for your bones and teeth.

X-rays and gamma rays have ultra-high frequencies that can travel through matter and damage cells.  They can penetrate most materials.  Doctors use x-rays to look at images of bones or internal organs.

Review:

1. What are electromagnetic waves?
2. Explain how radio waves work.
3. What type of wave do doctors use to look at images of bones?