Looking at a rainbow, what do you see?

The rainbow – with all of its myths and legends – is an indicator of the data astronomers examine.

Image of a Rainbow over Niagara Falls.
Public Domain | Image courtesy of U.S. National Oceanic and Atmospheric Administration.


Light is Radiative energy , which can be split into a spectrum . A spectrum is the light’s component colors or wavelengths. Light can be split into its component colors or wavelengths by using a prism or diffraction grating.

Light comes in particle bundles, called photons. These photons travel at 186,000 mi/s or 300,000 km/s (3 X 108 m/s) . The Speed of Light, c, is an absolute; you cannot go faster than c. (the speed of light).

Light also moves in waves . Particles moving in waves are referred to as an Electromagnetic wave ; a wave in which both electric and magnetic waves “interact” or vibrate. The Wavelength is the distance between adjacent peaks on the wave, and the wave’s Frequency is the number of peaks that pass a specific point in a second.

Image of light moving through a prism and creating a rainbow.
CC BY-SA 3.0 | Image courtesy of NASA / ESA.
Image of wavelength over time. Explanation is on the page text.
Image courtesy of Florida State College at Jacksonville.