Day 38: Flat -> Spherical Mirrors

Monday, 6 October 2014


To make up for several days when I forgot to take pictures, I took a ton today. Above is some student work. The prompt: hold a small 3″x5″ mirror in front of your face and sketch what you see. Back the mirror up to four different places and sketch each image. About three-quarters of my students claim they saw an image like the one above. Ok, not everyone saw the monkey-man in Step 5. But most claimed the more they backed away from the mirror, the more they saw of themselves.

We spent a bunch of time Thursday and Friday busting this misconception.

The next question on the lab was about where to hang a mirror so a 6′ and 5′ tall person could share it and see their whole bodies. Below is Gertrude, a 6′ tall punk rocker with an amazing mohawk. We learned a more formal version of ray tracing for this problem. I shoulda used more colors on this diagram to make light rays easier to differentiate.


Finally, we went outside with a concave mirror and a broken meter stick. Kids were so surprised at the results. At least half wanted to know what would happen to their hand if they put it where the meter stick was. I looked at them like they were crazy. “Do you really want to put your hand in a location that just set a meter stick ON FIRE?”

imageThis day last year: Instrument Presentations



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