colour filter

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Was Santa Claus a Real Person?

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Why Do We Eat Turkey on Thanksgiving?

John F. Kennedy as a boy with his family

What Did We Call America’s Elite Before the “1 Percent”?

Los Angeles Police Department wanted flyer on Elizabeth Short, aka the "Black Dahlia," who was brutally murdered in January 1947. The FBI supported the Los Angeles Police Department in the case, including by identifying Short through her fingerprints that

America’s 5 Most Notorious Cold Cases (Including One You May Have Thought Was Already Solved)

Rural Irish landscape, Sligo, Ireland.

Why Is Ireland Two Countries?

Thumbnail for flags that look alike quiz Russia, Slovenia, Iceland, Norway

Flags That Look Alike

Ethel Rosenberg arrested in August 1950. Photograph dated Aug. 8, 1950. American civilians executed for espionage. Spies, communists, Julius Rosenberg

Spies Like Us: 10 Famous Names in the Espionage Game

colour filter

optics

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optical engineering

In optics: Filters and thin films
A colour filter is a sheet of transparent material that modifies a light beam by selective absorption of some colours in relation to others. A neutral filter absorbs all wavelengths equally and merely serves to reduce the intensity of a beam of light without changing its…
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