The Electromagnetic Spectrum

The electromagnetic spectrum ranges from short wavelength, high frequency waves to long wavelength, low frequency waves.

The highest frequency waves are gamma rays, produced in exploding stars and through natural radioactive decay. X-rays have lower frequencies than gamma rays and are commonly used in medical imaging. Next come ultraviolet rays that are categorized as UV-B or UV-A. UV-B rays are higher frequency and are considered harmful, commonly being associated with skin cancer. UV-A rays are just beyond the violet part of the visible spectrum and are not considered harmful.  UV-A rays are produced by so-called “black” lights. The visible part of the electromagnetic spectrum is what we call light and ranges in wavelength from 400 to 700 nanometers. Violet light is higher frequency and red light is lower frequency.

Beyond red light we find infrared, which is often associated with heat, as it is readily absorbed and transmitted by most objects.

Microwaves have longer wavelengths than infrared and are commonly used for radar and some types of communications.

Last come radio waves, which have wavelengths that range from a few feet to the size of mountains.

Scientists are interested in observing all types of electromagnetic radiation from space, as each provides additional information about the processes within stars and help us understand the history of the universe.