optics.gif (6954 bytes)


RAYLEIGH SCATTERING
Why the Sky Is Blue and Sunsets are Red?

(This demonstration is no longer done.)






EQUIPMENT

    redball.gif (326 bytes) 5 L Plastic Water Tank
   
redball.gif (326 bytes) 18 g of Sodium Thiosulfate (hypo)
   
redball.gif (326 bytes) 10 ml of HCl
    redball.gif (326 bytes) 5 L of Distilled Water
   
redball.gif (326 bytes) Lamp




NARRATIVE
         The sky is blue and some sunsets are red because of Rayleigh Scattering of light from particles about the size of a wavelength of light. Before class, dissolve 18 g of hypo in 5 L of distilled water. (The solution will be cloudy). At or a little before the demonstration is to be done, stir in 10 ml of HCL. This will clear the solution. Precipitation of sulfur will begin anywhere from 30 sec to 3 minutes. Precipitation is essentially complete 2 to 5 minutes after it begins.