## Logarithmic ScalesThe chart below is designed to show the basic physical relationship between energy and electromagnetic radiation. A fundamental result of this relationship is that the smaller an object, the smaller is the wavelength of radiation required to form an image of it. Furthermore, the smaller the wavelength, the greater the energy required to produce it. This is why larger and more powerful accelerators are required to discover smaller and more energetic particles. The top row of bars indicates the source for electromagnetic radiation of a particular frequency range. The second row of bars gives the name associated with a specific range of frequencies. The next three lines are the three related scales of frequency, wavelength, and energy. The bottom scale provides the names of some commonly used units along the distance scale. Electromagnetic radiation with a wavelength of one
micrometer, lies just redward (longer wavelength) of what
the eye can see. It has a frequency of 3.00 x 10 ## Some Words About UnitsI have used the International System of Units (SI) throughout these pages--with some occasional exceptions. My intent is to be as accurate and consistent as possible while reaching a wide and varied audience. I hope to entertain, and possibly enlighten, nonscientists and scientists alike. For a thorough discussion of the International System of Units, check out the U.S. Metric Association. In particular: - Large numbers are written using numerals, with spaces marking off groups of three, not commas or periods: 3 275 789 or 0.000 005 6.
- Scientific notation is preferred over the use of billion or trillion
to avoid confusion between U.S., English, and Continental meanings:
3.0 x 10
^{9}is preferred over 3 billion (U.S.) or 3 thousand million (English). When I use billion I use the U.S. meaning.
The light year The orbital distance from the Earth to the Sun is defined as an astronomical unit (AU) and is approximately 150 Gm. Thus 1 light year is equal to about 67 000 AU. Copyright © 2016 by Bruce Bryson |