2006-11-11 02:50:45 · 2 answers · asked by Rosie 3 in Science & Mathematics ➔ Astronomy & Space
I am guessing you are asking a more basic question. Light spreads out as it propogates making stuff that is far away appear dimmer. Understanding the distance to something is therefore necessary to understand the total power production of a source. If light did not spread out, this would not be an issue in research.
The apparent brightness falls off by a factor of 1/d^2 where d is the distance between the observer and an unresolved ("point") source.
2006-11-12 09:46:17 · answer #1 · answered by Mr. Quark 5 · 1⤊ 0⤋
One type of astronomical instrument where beam spreading is important is in the production of "artificial stars" using laser beams. A laser beam is sent into the sky, and some of the light is reflected from the upper atmosphere. If this spot can be made small, then it can be used to correct for twinkling (seeing) of nearby star images. If the laser beam spreads, it doesn't work as well.
Many astronomical instruments are "diffraction limited", especially at longer wavelengths and radio. This means that the optical path design is dominated by beam spreading.
2006-11-11 03:18:40 · answer #2 · answered by cosmo 7 · 0⤊ 0⤋