The lesson was designed at the National Center of Atmospheric Research in Boulder Colorado. Research was done on the detection of ultra violet radiation and which leads to the presence of Tropospheric Ozone. Field testing of the lesson was needed and the eighth grade students of Blocker Middle School were very anxious to help. The module, with the UV radiation lab, was developed by eighth grade students for students of all ages. The ultra violet Frisbee is used in the experiment but the eighth graders wanted to know more about it.
In Ms. DeRulle's English class, the students wrote business letters to different companies. One of the companies was Wham-O, the manufacturer of the U.V. Frisbee. They wanted to know why the Frisbee turns a purple color when placed in sunlight.
One student sent a design to Wham-O for a UV Frisbee that would change color according to the degree of UV light coming through the atmosphere. The Photochemical cell in the polymers would vary through the Frisbee and would signal the user to make sure to wear sun block. Blocker Middle School students collaborated with budding young scientist in the first grade. They took what they found with the lesson and used it to teach younger students. This gave them a chance to see if their ideas in changing the lesson would work. They electronically mailed and wrote business letters to the scientists at NCAR, Wham-O, and to TV meteorologists about UV radiation. The students received a four page response from Wham-O as well as 2 large UV Frisbees for teachers.
They came to realize that the members of the business community will respond
enthusiastically to their letters. The eighth grade class wanted UV readings
announced on TV as a warning to the danger of skin cancer. Now you will find
UV index mentioned in the summer time on many channels. The following information
was given to the students via email and letters. It is essential information
for the lesson. Also, the classes are ninety minute block schedule which allows
for varied activities. The another lesson from the module can be found in Science
Teacher, December '95 " Ground Level Ozone Testing" and on the World Wide
Web at Center for Excellence in Education,
link to Super Science Links.
The energy from the sun includes not only visible light, but also wavelengths of light longer and shorter than the visible light. The wavelengths of visible light increase from the blue end of the spectrum and decrease towards the red. Just on the short side of blue is a wavelength of energy referred to as ultraviolet (UV). "Ultra" meaning beyond, so ultraviolet means beyond the violet. The amount of UV reaching the earth's surface depends on the distance it travels through the atmosphere. During morning hours, the path of the UV ray must travel through more of the earth's atmosphere because the sun is lower on the horizon. During the noon hours the rays travel a shorter distance through the atmosphere because the sun is directly overhead. The presence of UV in both the stratosphere and troposphere is important. The tonic water activity is a simple method of demonstrating its presence. The quinine in the tonic water absorbs the UV light which causes the it to fluorescence. Place a dark poster board or felt cloth behind the tonic water and tap water.
Place the prisms in the sunlight to see the spectrum. The students can see that white light is made up of all the colors in the spectrum. Point out the violet and explain the "Ultra" violet that caused the tonic water to glow blue. Our atmosphere acts as a filter for ultraviolet radiation. The students changed the part of the experiment that would demonstrate the different thicknesses of glass and /or plastic to show the filtering effect on the Frisbee. Instead of the building materials, they used different SPF factors of sun tan lotion. The color you of the Frisbee changes from a white to a deep violet depending on the amount of UV light it absorbs. The ozone layer in the stratosphere is absorbing UV radiation that would otherwise harm us. We are not as protected as we once were due to the ozone depletion. More harmful UV rays reach the earth's surface and can cause skin cancer. Humans now must find a way to filter the sunlight to decrease the chance of skin cancer.
Suntan lotion has an SPF number on them that stands for Sun Protection Factor. The higher the number, the more filter from UV light the skin has. Now show the different filtering effect of the suntan lotions on the Frisbee. A great deal of this lesson is depending on a sunny day. It can still be demonstrated during a rainy day. Use an ultraviolet lamp if have to stay inside the . Ask the students to name individuals they know that have skin cancer. Many students will know of someone that has or did have skin cancer. Explain that tanning beds are also dangerous. They damage the skin like the UV rays of the sun.