optical density


physics the former name for reflection density, transmission density


More Than Trippy: Our Favorite Viral Optical Illusions Explained
What’s not to love about optical illusions? The magical, mysterious, mind-bending visuals never cease to evoke a series of ‘“woahs” and “what the’s--.” Words usually fail to describe them. Yet, one common word that is often used is trippy, hearkening to the psychedelic days of the ‘60s and ‘70s. But, believe it or not, the first optical illusions emerged far earlier, in the 5th century B.C. They even had Aristotle bumfuzzled! From Medieval Latin, opticus means “of sight or seeing” and ludere, “to play”—thus, optical illusions are visuals that essentially “play with one’s sight.” Because these images are invested with such mysterious power, we think optical illusions are some of the coolest didactic devices known to man. They’re brilliant to look at, and they teach us to question everything. So, to honor these powerful images, we want to share with you their proper names—because, honestly, trippy only holds up in the basement. Get your brains and eyeballs ready. They will be boggled.
Are some languages really faster than English? Does that mean slower languages are less effective?
Think of when you’ve listened to someone speak Spanish or Japanese. Does it seem the words flow out very quickly, faster than other languages? Academics would agree with you. For the last decade, linguists have speculated that different languages are spoken at significantly different rates. The challenge has been how to measure the respective speeds. Recently, linguist François Pel­legrino along with his team at the …

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medicine definitions for optical density

optical density


The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.