Day 55: Divergent?

Monday, 31 October 


Gave the kids a triangular prism and asked them to predict where the light ray would emerge. Then we predicted the path of a laser as shined through a double convex lens and a double concave lens. (Oh and BTW, the GiphyCam app for your phone is amazing).

I then asked why they think the lenses are sometimes called converging and diverging.



2 thoughts on “Day 55: Divergent?

  1. Love the demos and the questions! A few questions for you:
    1. Do you talk much about the difference between B and C in the prism question?
    2. Do you think using lasers to demonstrate lens effects hurts them in understanding regular imaging at all? I guess I feel like it’s quite an abstraction compared to normal light. Don’t get me wrong, I do all the same things! I just sometimes wonder about it being too clean (and too much like the ray diagrams in the book) as opposed to the messy business of thinking of light striking every part of the lens (from every angle!) all at once.


    • 1. I don’t. Time gets the best of me. FWIW, the vast majority correctly pick D before trying it out. We also have a great opportunity to talk about the two different reflections that come out of the prism as well. Honestly, that’s more interesting to high school freshmen than the difference between B and C.

      2. Funny you should ask about the over-simplification of using lasers — a kid in class this morning asked me about just that issue. He was having trouble understanding how the whole image forms. How then could I show the infinite number of light rays from every point on an object that travel through a lens and reform at the image location?

      I’m gonna pay #NaBloCoMo forward and find a #teach180 post to comment on. Thanks!

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