Q & A
Acronym Guide
Further Reading
Outside the Site
Google Sky
Multimedia, Etc
Animation & Video
Special Features
Chandra Podcasts
Desktop Images
The Big Chandra Picture
Screen Savers
Web Shortcuts
Chandra Blog
RSS Feed
Email Newsletter
News & Noteworthy
Image Use Policy
Questions & Answers
Glossary of Terms
Download Guide
Get Adobe Reader
Q&A: General Astronomy and Space Science

What are the different types of EMR and what are they used for?

There are many kind of electromagnetic radiation and they are distinguished by their wavelengths if you consider EMR as waves.

You can also think of electromagnetic radiation as consisting of particles of light, called photons, and each photon has a certain amount of energy associated with it. Each energy corresponds to a different type of EMR. High energies correspond to short wavelengths.

Let's think of EMR as waves for our discussion. Scientists group together certain wavelengths into catagories, for example visible light is the group of wavelengths from 400 nanometers to 700 nanometers. This is the energy band (or grouping) that our eyes are sensitive to.

Shorter wavelengths are grouped together as ultraviolet radiation, the band that gives us sunburns! And even shorter wavelengths are grouped together as x-rays. X-rays can be used in many different ways, but 2 of the most important ways are medical x-rays and x-ray telescopes like Chandra.

For a medical x-ray, a beam of x-rays is sent towards a human being (let's say towards a tooth) and a special plate is set behind the tooth to catch the x-rays after they pass through. This gives a picture of the tooth including any cracks or cavities in it. So it is a type of x-ray picture.
More at

X-ray telescopes on the other hand are big x-ray buckets, catching x-rays that are emitted from objects in the universe. Since x-rays have short wavelenths, and therefore high energies, telescopes like Chandra are most sensitive to hot (high energy) objects and processes.
More at

An example of longer wavelength EMR is the group we call radio waves, which are familiar to you from listening to the radio.

Another explanation of this may be found on a NASA website at:

Back | Index | Next