What Causes an Electromagnetic Wave?
Electromagnetic waves are made by a vibrating electric charge. As in the name, these waves consist of a magnetic and electric component.
Electromagnetic vs. Mechanical Waves
Where electromagnetic (EM) waves can travel through both a vacuum or a medium, mechanical waves can not. Mechanical waves require a medium a to travel through. Also, EM waves are often described as a disturbance, and mechanical waves are known as a periodic disturbance.
NASA - Tour of the Electromagnetic Spectrum
Types of Electromagnetic Waves
Radio waves have the longest wavelength of the EM waves described here as well as lower frequencies than microwaves. With a length of over 1 mm, they have the lowest energy and are associated with the lowest temperature. Radio waves are used to transmit EM radiation, which is then decoded and turned into sound so that we can listen in on our favorite stations. Radio waves are also used for communication, especially for aircraft and are even emitted by stars.
Microwaves have higher frequencies than radio waves as well as lower energy, but they have longer wavelengths. Microwaves are obviously used for cooking, but there are other uses. Cell phone communication is through microwaves. Astronomers can also use microwaves to learn about nearby galaxies.
Infrared waves have wavelengths spanning from 710 nm to 1 mm. The frequency and energy of infrared waves is higher than that of microwaves. Our bodies give off infrared waves at a wavelength of no more 900 nm. Night vision goggles spot the infrared waves given off by our bodies. Infrared waves are also used to map the dust between stars. This dust is either carbon or silicates that can be found between stars.
Visible Light Waves
The wavelengths of visible light waves span from 400 to 700 nm long. Following the pattern, visible light waves have a higher frequency and energy than infrared waves. Visible light waves are of course, visible light waves which are one of the few parts of the EM spectrum we can see. We perceive the visible light from the sun as the colors of the rainbow. Other examples of things that give of visible light are fireflies, light bulbs, and stars(like the sun).
Ultra-Violet (UV) waves have wavelengths of 10 to 310 nm. Their frequency and and energy is higher than visible light waves. UV waves is mainly found in sunlight but is also used sun beds, security pens, and fluorescent lights. Young stars like in the picture create a lot of UV waves.
The frequency and energy of x-rays is higher than UV waves, and the wavelength is shorter ranging from .01 to 10 nm. X-rays pas through soft tissue but do not pass through bone or metal which is why they are used to image things like teeth, broken bones, or looking through your baggage at an airport. X-rays are also found in the gases emitted from exploding stars.
Gamma rays have the smallest wavelength of under .01 of a nanometer but they have the highest frequency and energy of the EM waves discussed here. Gamma rays cannot be seen or felt, and like x-rays they pass through most skin and soft materials but are absorbed by some cells. Gamma radiation is used to sterilize equipment, kill harmful bacteria in food, and kill cancer cells. Gamma waves can be found in things such as black holes and pulsars, a highly magnetized neutron star. The hulk was created by absorbing too many gamma rays.