Another very important point about light is the ENERGY it carries. We know from our own experience that Gamma Rays and X-Rays are very dangerous. They have very HIGH frequencies, and very SHORT wavelengths. The Energy associated with a particular photons depends on its wavelength (or frequency):



(Here, ``h'' refers to Planck's Constant)

We will find that astronomical sources that put out a lot of high energy light, such as Gamma-Rays, X-rays or Ultraviolet light, are usually very HOT , while sources emitting in at long wavelengths, infrared and radio, are usually very COLD.





BUT How is light CREATED?

We will study two main physical processes which create LIGHT in the Universe. Understanding HOW these processes occur is vitally important to our interpretation of astronomical sources.


1) BLACK BODY RADIATION


2) ATOMIC & MOLECULAR TRANSITIONS