Refraction\Visible Spectrum

Demonstration

The following demo may be used for Ch. 9-1 pertaining to the visible spectrum or Ch. 10-1 pertaining to the refraction of light rays.

Blue Sky-Red Sunset

Why is the sky blue and why does it turn red as the sun sets?  To demonstrate why this happens, fill a beaker with water.  Using an overhead projector, project the beaker onto your screen.  Add 10mL of concentrated sulfuric acid and stir.  Next add 10 mL photographic fixer, which is triosulfate.  The reaction produces a small precipitate.  As the reaction between takes place, the water in the beaker turns blue, but the projected solution on the screen is red.  This occurs because the shorter blue wavelengths are scattered by the precipitate while the longer red wavelength pass through.

Blue Sky - Red Sunset