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| Google Doodle, 2/22/2012 |
Today's Google Doodle is an animated gif celebrating the birthday of
Heinrich Hertz . Writing this post probably won't hurtz me much. Hertz. The SI unit of frequency in cycles per second is named after him (hertz, Hz) in honor of his research on electromagnetics - specifically the existence of free-space propagation of EM waves at radio frequencies. He also established the photoelectric effect (PE) after noticing changes in the charge of objects illuminated by UV light. The PE effect was later explained by Albert Einstein. Hertz also experimented with "cathode rays" and showed they could penetrate thin sheets of aluminum.
Frequency (or more precisely temporal frequency) is a fundamental physical idea. All kinds of objects vibrate , more or less, periodically - leaves flutter in the wind, hollow tubes whistle, trees sway, balls bounce. etc. etc. Surface waves move water up and down and move foward and backward. The
frequency spectrum of a time-domain function is a unique
transformation (the Fourier transform). Time and frequency are dual variables related through an
analytic duality. Here is a
list of dualities. The one of interest here is
Pontryagin duality .
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