Monday, March 19, 2018

a monday matinee...

3 comments:

John Wells said...

East windowsill in the morning. While the term Radiometer can refer to any device that measures electromagnetic radiation (e.g. light), the term is often used to refer specifically to a Crookes radiometer ("light-mill"), a device invented in 1873 in which a rotor (having vanes which are dark on one side, and light on the other) in a partial vacuum spins when exposed to light. A common belief (one originally held even by Crookes) is that the momentum of the absorbed light on the black faces makes the radiometer operate. If this were true however, the radiometer would spin away from the non-black faces, since the photons bouncing off those faces impart more momentum than the photons absorbed on the black faces. Photons do exert radiation pressure on the faces, but those forces are dwarfed by other effects. The currently accepted explanation depends on having just the right degree of vacuum, and relates to the transfer of heat rather than the direct effect of photons. News Theme 2 by Audionautix is licensed under a Creative Commons Attribution license (https://creativecommons.org/licenses/...)
Artist: http://audionautix.com/ Anton by Dan Bordan used by permission from the YouTube Audio Library.

Margery Bills said...

You had this on before. Where did you get your Radiometer?

WestTexas Educator said...

This calmed me.. I needed it.