AstronomyOnline.org
home observation science solar system stars our galaxy cosmology astrobiology exoplanets astrophotography
Science
icon Introduction
icon Astronomy Tools
Concepts
1. Electromagnetic Spectrum
2. Atmosphere Limitations
3. Space Observations
Equipment
1. Telescopes
2. Radio
3. Space Tools
4. Photography
5. Spectroscopy
6. Computers
7. Advanced Methods
8. Radio Astronomy
icon Basic Mathematics
Algebra
Statistics
Geometry
Scientific Notation
Log Scales
Calculus
icon Physics
Concepts
- Basic Units of Measure
- Mass & Density
- Temperature
- Velocity & Acceleration
- Force, Pressure & Energy
- Atoms
- Quantum Physics
- Nature of Light
Formulas
- Brightness
- Cepheid Rulers
- Distance
- Doppler Shift
- Frequency & Wavelength
- Hubble's Law
- Inverse Square Law
- Kinetic Energy
- Luminosity
- Magnitudes
- Convert Mass to Energy
- Kepler & Newton - Orbits
- Parallax
- Planck's Law
- Relativistic Redshift
- Relativity
- Schwarzschild Radius 
- Synodic & Sidereal Periods
- Sidereal Time
- Small Angle Formula
- Stellar Properties 
- Stephan-Boltzmann Law
- Telescope Related
- Temperature
- Tidal Forces
- Wien's Law
Constants
icon Computer Models
icon Additional Resources
1. Advanced Topics
2. Guest Contributions
Concepts - The Electromagnetic Spectrum

The electromagnetic spectrum (also called the EM-band) contains gamma rays, radio waves and everything in between. The history of discovering the electromagnetic spectrum is a fascinating one. Sir Isaac Newton used a prism to split sunlight into its fundamental colors of the rainbow.
Sir William Herschel discovered, by accident, the infrared portion of the spectrum when he placed thermometers above the red portion of a projected spectrum. The image on the left shows how this was confirmed, with one of the three thermometers places above the red portion of the spectrum

Johann Ritter suspected "invisible" light on the opposite (blue) end of a spectrum and used paper soaked with silver chloride to detect it. Thomas Young confirmed the wave nature of light (that light moves like waves similar to ocean waves) by examining diffraction patterns through slits.

Michael Faraday and James Maxwell collaborated together to theorize the electromagnetic nature of light - that is changing the electric current in the wave alters its magnetic field. The image below (don't laugh, I'm still learning Adobe Illustrator!) demonstrates how the magnetic portion of this wave is 90o to the electric portion of the wave - hence 'electromagnetic.'

Experimenting with "Maxwellian Waves," Heinrich Hertz discovered radio waves. Wilhelm Rontgen discovered X-Rays while seemingly serendipitously experimenting with electric current through cardboard tubes with exposed film he had on the other end of the room - he saw the bones of his hand.

It wasn't until Albert Einstein, winning the Nobel Prize for discovering the photoelectric effect, that the wave-particle duality of electromagnetic waves was understood.

Eventually, a tool was created in the form of the electromagnetic spectrum.

As a starting point for understanding the spectrum, visible light covers only a small part - 400 nanometers (blue) to 700 nanometers (red).

The image below is a graph from the Chandra website demonstrating the entire electro-magnetic spectrum. Notice that only a very small portion of this spectrum (in the middle) is made up of visible light.

Back to Top

Search | Site Map | Buy Stuff - Store | Appendix
©2004 - 2013 Astronomy Online. All rights reserved. Contact Us. Legal. Creative Commons License
The works within is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.