December 1, 2010 Issue

Physics To Go 109 - Imaging Air

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Physics in Your World

Wikipedia: Shadowgraph image
Image credit:  Andrew Davidhazy, Rochester Institute of Technology

Wikipedia: Shadowgraph

This is a Schlieren image, which reveals differences in the density of air above the candles. To find out more about these images, visit Wikipedia: Shadowgraph, and to learn how to make one, visit Schlieren Photography Principles.

- Making one of these images is more complicated than making a shadowgraph, such as the image in From Physics Research.
- For more high-speed images by Andrew Davidhazy, visit this page.

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Physics at Home

Doppler Physlet

Security note:
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.

Try the Physlet simulation from Davidson College to investigate the shockwaves and Doppler effect produced by objects moving at various speeds--in particular, at speeds below and above the speed of sound.


From Physics Research

The Doppler Effect and Sonic Booms image

The Doppler Effect and Sonic Booms

This image of the shockwave made by a speeding bullet is a shadowgraph--simply a photograph of the shadow of the bullet and the shockwave. Variations in the density of air refract the light used to make the shadow and produce bright and dark regions.

- Note the little fragment that is moving just below the speed of sound (the disturbance is slightly ahead of it).
- To see animations of shockwaves made by objects moving at various speeds, visit The Doppler Effect and Sonic Booms (skip right to the animations).

Worth a Look

Physics in Action: Sonic Shock

For more on shockwaves, and how engineers have insulated space vehicles from the shockwave's heat, visit Physics in Action: Sonic Shock.

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