Special Frisbees Detect Ultraviolet Radiation

Background

Solar ultraviolet radiation can cause damage to eyes, skin, crops and wildland plants, and many manufactured substances (paints, plastics, etc.). Since the damaging effects of UV radiation were first discovered, many substances have been developed to act as UV radiation shields. Sunscreen creams and UV-absorbing sunglasses are two of the most obvious examples intended to protect people. Other substances are marketed, however, that are intended to shield objects. For example, automobile finishes and house paints usually contain UV-absorbing chemicals that are intended to prevent fading due to chemical changes brought about by UV exposure. Plastic lawn furniture, rubber garden hoses, or any similar object intended to be exposed to the sun for long periods are often treated to reduce UV damage. Without such protection, plastic and rubber objects will become brittle and crumble after extended exposure in sunny climates.

Through classroom demonstrations and experiences, you've become familiar with the reaction of UV-sensitive Frisbees to ultraviolet radiation from the sun. In this investigation, you will use the UV sensitivity of the Frisbee to help you judge the effectiveness of different materials in acting as UV shields.

Procedure

  1. You will be provided with an assortment of materials intended to act as UV shields, UV-sensitive Frisbees or pieces of Frisbees to act as your UV sensors, access to a clear, sunlit area for your tests (or access to a UV light provided by the teacher.)

  2. Working alone or with a partner according to your teacher's directions, develop a good, logical, and specific question about the effectiveness of UV shields that you can answer by performing a careful experiment using the materials provided. For example, you might wonder which moisturizing face cream acts as a better UV shield, or what sort of plastic sheeting would make a better greenhouse cover to reduce UV exposure on greenhouse plants. It's important to ask a very specific question that makes sense and that is answerable with the materials and time you have available. It wouldn't make sense, for example, to ask "How is UV stopped?" or "What's the best UV shield on earth?" because you can't answer either of these questions in this experiment.

  3. Once you have a good question, show it to your teacher for approval.

  4. Next, design an experiment to answer your question. Determine what materials you need, how much time you'll need, and how you will be collecting the data. Remember that your experiment must include a control and replicates (i.e., must be replicable).

  5. Show your experimental design to your teacher for approval before you proceed, then carry out the experiment, taking careful notes on what you do, how you do it, and the data that you collect.

  6. Report the results of the study according to your teacher's instructions.

When you're finished with the activity, click on Back to Teacher Guide at the top of the page.