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  • Writer's pictureCarolyn Balch

Dollar Store Optics

I love science experiments, and I love sharing these with my children and my students. When I returned to the classroom after raising my kids and spending a stint in museum education, I knew I wanted to bring the fascination of hands-on exhibits to our learning.

Rather than use a packaged curriculum, we shaped our learning around experiments and explorations that we did every day. We started with themes and topics that connected to their humanities studies and branched out from there. As I began to curate a collection of experiments and explorations, I asked myself a few questions…

Value: Is the concept essential to our course of study?

Appropriateness: Can my students understand the science behind this activity?

Thoughtful: Does it make me think and ask intriguing questions about what’s going on?

Authentic: Is it similar to real science done by scientists or can I change it so that it is?

Engaging: Is this something I find interesting and want to spend time on?

Observations: Is something interesting happening or is there something worth looking at?

Data: Is there something I can measure or collect?

Repeatability: Can I do this over and over with the same results?

Fit: Is this the best experiment for investigating this phenomenon?

Complexity: Can my students follow the directions successfully?

While no experiment satisfies each of these parameters, most address more than one. For me, the first three are key factors, and if an activity fails on any of these, I’ll keep looking for a better fit.

Here’s a simple idea that would pass our test:

How can a lens make an image?

Find a convex lens, which is the type used in magnifying lenses and reading glasses. You’ll need a light-colored, flat surface to act as a screen (a blank wall works fine) but if you want to be mobile, a piece of poster board or a lid to a plastic bin will also work well.

Place yourself in a dim, shadowed area where there’s a bright light or window nearby. Hold the lens up to the screen so that it’s between the bright window and the screen. Move the lens back and forth until you see an image come into focus. (If your screen is in bright light, the image will be there, you just won’t be able to see it since the ambient light will wash it out).

Once you’ve mastered this, you can investigate further. Determine whether the image is flipped in any way. Figure out if the image is smaller or larger than the object. Can you tell if the image is brighter or dimmer than the object? You can also try other lenses (different powers and sizes) and see how they compare to the first one you investigated.

How can a clear piece of glass cast a shadow?

Find a concave lens, which is the type used in glasses needed for a nearsighted person. Find a blank wall or other screen and some type of light to shine on the screen. Hold the lens so that it is between the light and the screen and see what you see. Try to make an image as you did with the previous lenses. What do you notice now?

If you’re interested in a more formal approach, you can check out this activity, which is part of a complete curriculum on light.

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