Demonstration of an optical technique that allows us to see small changes in the index of refraction in air. A point source of light is reflected from a concave mirror and focused onto the edge of a razor blade, which is mounted in front of the camera. Light refracted near the mirror and intercepted by the blade gives the illusion of a shadow.
Seen here are the heated gases from a candle flame and a hair dryer, helium gas, and sulfur hexafluoride gas.
More information on our setup.
Note that this version of the setup uses a white LED flashlight instead of an automotive light bulb.
Wednesday, 29 January 2014
Rays in the universe: radon
The earth contains a great many natural radioactive elements (such as uranium, thorium and potassium). Uranium, for example, is present in all rocks, and in particular granite rocks. When it decomposes, it gives rise to a radioactive family, ultimately forming lead, which is stable. Radon is one of the radioactive decay products of uranium. Its distinguishing sign is that it is a gas.
And as it is a gas, it escapes and accumulates in caves or galleries, which are enclosed spaces. During the first few years when French uranium deposits were mined, the miners breathed air in which the radon content could be as high as 20,000 Becquerels per cubic meter. Epidemiological studies on uranium miners have shown that radon is a carcinogenic agent that can cause lung cancer. More recently, studies on the general population have confirmed this risk for exposure to radon in the home.
And as it is a gas, it escapes and accumulates in caves or galleries, which are enclosed spaces. During the first few years when French uranium deposits were mined, the miners breathed air in which the radon content could be as high as 20,000 Becquerels per cubic meter. Epidemiological studies on uranium miners have shown that radon is a carcinogenic agent that can cause lung cancer. More recently, studies on the general population have confirmed this risk for exposure to radon in the home.
Tuesday, 28 January 2014
The Dynamics of an Elevator Ride
We go for a short ride in the elevator and record the acceleration for display.
How fast are you moving right now? - Tucker Hiatt
View full lesson: http://ed.ted.com/lessons/how-fast-are-you-moving-right-now-tucker-hiatt
"How fast are you moving?" seems like an easy question, but it's actually quite complicated -- and perhaps best answered by another question: "Relative to what?" Even when you think you're standing still, the Earth is moving relative to the Sun, which is moving relative to the Milky Way, which is...you get the idea. Tucker Hiatt unravels the concepts of absolute and relative speed.
Lesson by Tucker Hiatt, animation by Zedem Media.
"How fast are you moving?" seems like an easy question, but it's actually quite complicated -- and perhaps best answered by another question: "Relative to what?" Even when you think you're standing still, the Earth is moving relative to the Sun, which is moving relative to the Milky Way, which is...you get the idea. Tucker Hiatt unravels the concepts of absolute and relative speed.
Lesson by Tucker Hiatt, animation by Zedem Media.
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