Image credit: Michael Smith, Institute for Biodiagnostics, Winnipeg, Canada; image source; larger image
Lasers light up blood-flow dynamics
If you shine a laser beam at a small angle to a piece of white paper, so the beam spot spreads out, you'll see what is called a speckle pattern (do this experiment with adult supervision). If you shine the beam on your skin, you'll see a different kind of pattern.
The image shows how laser speckle imaging can show the difference between normal blood flow, in the finger on the left, and increased blood flow due to the warming of the skin (the figure on the right was immersed in hot water). To find out more, see Lasers light up blood-flow dynamics and also this article from the National Research Council Canada.
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PhET Simulation: Lasers
Once you have clicked on the "simulation" link below, be sure to read the Java Security Advisory before running the simulation: To do that, click the "Read now" button on the yellow band near the top of the PhET page.
See if you can produce a laser beam in this simulation from the University of Colorado. Excite the laser's atoms with lights of different wavelengths and control components of the laser to create the beam.
(This feature was updated on May 5, 2013.)