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
Physics - Formulas - Inverse Square Law

The brightness of an object decreases dramatically as we move farther from the source. The result is due to a larger "sphere" of influence. Light from a source like a star shines in all directions, to the area of illumination increases with increasing distance so the total brightness thins out.

This is called the Inverse Square Law:

If we know the distance to a star, we can use this equation to determine its brightness.

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.