PURPOSE: To demonstrate that microwaves will pass through material through which light cannot pass.
DESCRIPTION: Demonstration M7-31: TYNDALL'S EXPERIMENT - COLLOIDAL SUNSET is used to show how increasing densities and increasing sizes of colloidal suspension particles first scatter out the blue, then eventually the red light. However, as the sulfur particles in the colloidal suspension grow and become more dense, the 12 cm wavelength microwaves remain virtually unaffected, which can be shown using the setup photographed.
This demonstration shows that certain wavelengths of electromagnetic waves are more useful than others in observing distant galaxies because of their ability to penetrate intergallactic materials and othe light-absorbing materials.
SUGGESTIONS:
REFERENCES: (PIRA unavailable.)
EQUIPMENT: Bright point source with condenser and iris, water tank with mirror, screen, and previously prepared chemicals from Demonstration M7-31: TYNDALL'S EXPERIMENT - COLLOIDAL SUNSET, microwave transmitter and receiver with overhead projector microammeter..
SETUP TIME: 5 min.
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