A Quick Introduction to LIGHT
Light: What IS it?
-
It's made up of oscillating electric and magnetic fields.
This is why we refer to it as electromagnetic radiation
YOU are a great "Detector" of Light: UV (skin response), optical (eyes), infrared (nerve endings under skin).
It's really an amazing thing!
-
Travels without any medium---important in astronomy! Imagine how little we would
know of the universe if Light needed a 'medium' to travel?
Travels very fast (``c'' = 300,000 km/s) Fast enough you don't notice its finite speed in day to day life. But in Astronomy, we DO notice it.
-
Moon to earth in ONE SECOND!
Earth to Sun ? About 8 minutes
Outer Solar System ? Pluto/Neptune orbit: About 5.5 hours.
Nearest Star? Alpha Centauri, 4 *light years* away.
Comes in a variety of Flavors:
| Name | Energy? | Wavelength? | Frequency? |
| Gamma-rays | VERY high | VERY short | VERY high |
| X-rays | very high | very short | very high |
| Ultraviolet | high | short | high |
| Optical | medium | medium | medium |
| Infrared | low | long | low |
| Microwave | very low | very long | very low |
| Radio | VERY low | VERY long | VERY low |