The Electromagnetic Spectrum . . .
(see textbook pages 484, 674 & 675)
(Since the textbook barely covers this topic, also see http://missionscience.nasa.gov/ems/02_anatomy.html)
. . .is a classification system that labels ranges of electromagnetic waves based on wavelength & frequency.
Ranges = 1 - radio waves
2 – microwaves
3 - infrared waves
4 - visible light waves
5 - ultraviolet waves
6 - x-ray waves
7 - gamma waves
* Waves carry energy. They do NOT carry atoms (i.e. matter)
*All waves start with a disturbance or vibration.
*There are two types of waves: Mechanical & Electromagnetic
1. Mechanic Waves - need a medium (i.e., matter) through which to travel.
Can be: 1. compressional &/or longitudinal waves – energy travels parallel to the vibration
Examples = Sound waves and Seismic P waves
2. Transverse Waves = energy travels perpendicular to the vibration
Example = Seismic S Waves
2. Electromagnetic Waves - do not need a medium because they carry energy by the continual
interaction between the electric and magnetic fields once the wave has been started.
All Electromagnetic Waves travel at the same speed through space, the speed of light, which is why they are
all called light waves. (The speed of light = 300,000 km/sec or 186,000 miles/sec.)
Diagram of Electromagnetic Spectrum
Diagram of Transverse Wave
**The diagram above is better than the one on page 484 because it shows the different groups of waves
originating separately rather than inferring that a gamma wave can turn into a radio wave over time.
Frequency = The # of waves occurring in one second and is recorded in units called Hertz.
Wavelength = the distance between a point on a wave and that same point where the wave begins to repeat
itself, such as from the crest to the crest or the trough to the trough.
Different elements emit different light waves. They have a signature fingerprint spectra.
* We can analyze a star’s spectra and tell what that star is made of (its composition).
* When we are looking at the star light that is traveling across space we are sometimes looking at something
that happened billions of years ago and the light has just reached us now.
* Each student should also have notes from the video clip on the uses of each type of wave in the
Electromagnetic Spectrum.