Definition: opacity: A property of matter that prevents light from passing through it. The opacity or opaqueness of something depends on the frequency of the light. For instance, the atmosphere of Venus is transparent to ultraviolet light, but is opaque to visible light.
opacity
by Nick Greene
for About.comFree Email Courses
Explore Space / Astronomy
Must Reads
About.com Special Features
A Smarter Future
Tips that will help finance your education, excel in the classroom, and advance your career. More >
How to Ace the GRE
Being well prepared is the first step; here are more essential suggestions. More >
©2009 About.com, a part of The New York Times Company.
All rights reserved.