Today you get to concentrate light, specifically the heat, from the Sun into a very small area. Normally, the sunlight would have filled up the entire area of the lens, but you’re shrinking this down to the size of the dot.
Magnifying lenses, telescopes, and microscopes use this idea to make objects appear different sizes by bending the light. When light passes through a different medium (from air to glass, water, a lens…) it changes speed and usually the angle at which it’s traveling. A prism splits incoming light into a rainbow because the light bends as it moves through the prism. A pair of eyeglasses will bend the light to magnify the image.
Materials
- Sunlight
- Glass jar
- Nail that fits in the jar
- 12” thread
- Hair from your head
- 12” string
- 12” fishing line
- 12” yarn
- Paperclip
- Magnifying glass
- Fire extinguisher
- Adult help
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Download Student Worksheet & Exercises
- You’re going to concentrate the power of the Sun on a flammable surface.
- Please do this on a fireproof surface! This experiment will damage tables, counters, carpets, and floors. Do this experiment on a fireproof surface, like concrete or blacktop.
- Hold the magnifier above the leaf and bring it down toward the leaf until you see a bright spot form on its surface. Adjust it until you see the light as bright and as concentrated as possible. First, you’ll notice smoke, then a tiny flame as the leaf burns.
- You are concentrating the light, specifically the heat, from the Sun into a very small area. Normally, the sunlight would have filled up the entire area of the lens, but you’re shrinking this down to the size of the dot that’s burning the leaf.
- Thermoelectric power plants use this principle to power entire cities by using this principle of concentrating the heat from the Sun.
- Never look through anything that has lenses in it at the Sun, including binoculars or telescopes, otherwise what’s happening to the leaf right now is going to happen to your eyeball.
- Now for the next part of the lab, do not use water bottles – you want something that doesn’t melt, like a glass jar from the pickles or the mayo.
- Remove the lid and punch a hole in the center. Use a drill with a ¼” drill bit or smaller, or a hammer and nail.
- Screw the lid on the jar.
- Tie one end of the thread to the paperclip.
- Poke the other end of the thread inside the hole on the lid.
- Unscrew the lid and tie a nail to the other end of the thread. You want the nail to be hanging above the bottom of the jar by an inch or two, so adjust the height as needed.
- Bring your jar outside.
- Question: Without breaking the glass or removing the lid, how can you get the nail to drop to the bottom of the jar?
What’s Going On?
Magnifying lenses, telescopes, and microscopes use this idea to make objects appear different sizes by bending the light. When light passes through a different medium (from air to glass, water, a lens…) it changes speed and usually the angle at which it’s traveling. A prism splits incoming light into a rainbow because the light bends as it moves through the prism. A pair of eyeglasses will bend the light to magnify the image.
Exercises
- What happened to the leaf? Why?
- How did you get the nail to drop?
- Which material ignited the quickest?
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