Friday, 11 October 2013
Give the kiddos a small mirror like above and ask them to draw what they see when the mirror is placed at 4 different distances from their face.
Almost to a person, I get this — as you back the mirror away, you’re able to see more of your face. (For my math friends who may not realize — your distance from the mirror doesn’t change your view. I dunno why, something to do with similar triangles, kidding!)
I don’t have a great way to go about the “are you sure?” bit. I ask to see their sketches. When I see the above, I ask the kids to show me. They slowly move the mirror from a few inches from their faces to arms-length. The kids swear up and down that they’re getting a view of more of themselves. Every so often (as in, 2-3 kids per class of 15), I’ll get someone arguing with her lab partner that no, the view stays the same as the mirror backs away from their face.
Next year, I’m considering doing the same exercise but with a ruler in the field of view — maybe if the kids have to quantify the field of view they’ll be less likely to see something they don’t.
Footnote: in September, one of my tweeps linked to an article about how students’ misconceptions can lead them to see results in the lab that aren’t true. That’s absolutely what happened here. I want to link to the article.
Do you know what I’m referring to and can you leave me a little link love in the comments? Update: It was Frank. Here’s the article: “Role of physics lecture demonstrations in conceptual learning“