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UV Bead Bracelets

In this activity, students make an Ultra-Violet (UV) light detector.

One type of light radiating from the sun, called ultraviolet (UV) light, is visible to insects and birds, but not to humans. UV radiation helps us make vitamin D in our skin, but too much of it can cause radiation burns (sunburns) and skin cancer.

Unlike plants, humans don't needs photosynthesis to make our food and survive, but the sun is still very important for us. Among other things, humans need the sun to help our skin make vitamin D. Without vitamin D our bones cannot grow properly and they get soft and bend, causing the bone malformation called Rickets.

How can you tell if UV radiation is present?

Human skin will change colour when it is exposed to enough (or too much) UV radiation. Unfortunately, it can take a few hours for a tan, or burn, to show. UV Beads allow detection of UV radiation through a colour change, before damage could be caused to a living organism.

UV beads have special chemicals that change colour very quickly when UV light hits them. Shadow, clothing, sunscreen, and sunglasses can block some UV light so the beads change colour more slowly if they are covered with one of these methods.

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Objectives

  • Explain that a chemical reaction can produce luminescence via the release of energy.

Materials

Key Questions

  • What makes the beads change colour?
  • What sources of light can include UV wavelengths?

What To Do

  1. As a demo to introduce this program, show the beads in the baggies. Demonstrate how beads change from white to coloured when exposed to UV light.
  2. Distribute bracelet string to students. Have students tie a knot at one end.
  3. Thread the beads on the string until desired length. Tie another knot to prevent the beads from falling off.
  4. Explore UV light in our environment using the colour change of the beads to indicate the presence of UV rays.

Extensions

  • Sunscreen is meant to protect your skin by blocking UV light. Put sunscreen on your beads and see whether they still turn colour. Do the beads turn colour on a cloudy day?
  • Try activating the beads with a black light or sunlight and “blocking” UV rays with sunglasses or other materials.