Say whether the Tyndall effect is the cause of what we see…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Say whether the Tyndall effect is the cause of what we see. Give a short reason each time.
- The beams of car headlights show up in fog.
- A laser pointer's beam cannot be seen from the side in clean air.
- Shafts of sunlight show through the trees on a misty morning.
- A torch beam cannot be seen inside a clear sugar solution.
Need a reminder? The key ideaShow
Very small particles, such as air molecules, scatter light in proportion to : blue far more than red. Large particles, such as cloud drops, scatter all colours about equally, which looks white. The Tyndall effect is the path of a beam made visible by scattering.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Yes: fog droplets scatter the light toward your eye.
Step 2. (b) No: there are no particles to scatter it sideways.
Step 3. (c) Yes: the droplets of the mist scatter the sunlight.
Step 4. (d) No: the particles of a true solution are too small.
Answer: (a) and (c) yes; (b) and (d) no.
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