Light Scattering
Light scattering is what happens when light bounces off tiny things in its path, like dust or water drops.
When flour dust floats in the air above a mixing bowl, a beam of sunlight hits the tiny particles. Each particle sends the light off in a different direction. This makes the whole cloud glow, not just the spot the beam hit first. The light spreads out through the dust the same way it spreads through fog or haze.
Explaining light scattering by grade level
Shine a flashlight through a glass of foggy water. The beam shows up because tiny bits in the water bounce the light around. Blue light bounces more than red light. That is why the sky looks blue on a clear day.
Projects that explore light scattering
Blue light has a shorter wavelength than red, so it bounces off gas molecules in the atmosphere more easily. You can see this effect at home. Add a little milk to a glass of water and shine a flashlight through it in a dark room. The water looks bluish from the side, where the scattered blue light reaches your eyes. Look straight at the light source and it appears reddish, because blue has already bounced away and longer wavelengths are what remain.
Light scattering changes with distance. When you shine a flashlight into a clear glue stick, the end near the light glows blue because short blue waves bounce off tiny particles first. The far end glows yellow-orange because blue light has already scattered away, leaving longer wavelengths to pass through.
Some wavelengths pass through a foggy liquid with less scattering than others. Fill a jar with water, stir in two teaspoons of milk, and shine a flashlight through it covered with different colors of cellophane. A light meter behind the jar records the brightness each time. Yellow light measured 8.8 lumens, the highest reading. Orange came close at 8.4. Blue scored lowest at 6.3. Longer-wavelength colors pass through with less scattering.