Answers

2015-02-28T18:58:25+05:30
A measure of the extent to which a substance transmits light or other electromagnetic radiation is known as optical density. 2. The act or process of propagating, especially the process by which a disturbance, such as the motion of electromagnetic or sound waves, is transmitted through a medium such as air or water.
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2015-02-28T19:16:46+05:30
See 
Optical Density (OD) is a way to describe or make you understand the blocking ability of an optical filter or a speacilly designed object
propogation mens it can be transmission of uv,iv magnetic rays etc
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