The goal is to have the student test an initial hypothesis about UV light penetration by conducting a controlled experiment. The experiment will also provide an opportunity for the student to learn about the differences between UVA and UVB in the ultraviolet spectrum.
- What is the effect of fabric thickness on UV transmission?
- What is the effect of tightness of weave on UV transmission?
- What is the effect of fabric weight on UV transmission?
- What is the effect of fabric type on UV transmission?
- What is the effect of fabric colour on UV transmission?
- Is it possible to stop all UV radiation with the tested commercial fabrics?
With depletion of the earth’s ozone layer, more ultraviolet radiation from the sun is reaching the surface of the earth. This radiation can produce a painful sunburn or contribute to skin cancer if your skin is not protected. UV-light sensitive beads that change colour can be used to evaluate how well different types of fabric block UV radiation.
- Assorted fabrics, UV detection beads, digital caliper; kitchen scale
- WFabric (used clothing store), UV beads (hobby store, Internet), caliper (Walmart type store), kitchen scale (Internet, Walmart-type store)
- Conduct a background literature search about UV radiation. Based on your own experience with sunburn, formulate a hypothesis to predict which kinds of fabrics will provide the most protection from ultraviolet radiation.
- Collect a variety of used or discarded fabrics. Cut uniform-size fabric samples. Be sure to select fabrics having different thicknesses, weave tightness, weights, types of fiber, and colors.
- Weigh each of the samples, and measure the thickness. Record this information, along with observations about weave characteristics, type of fiber, and colour in your notebook.
- Expose the UV-sensitive beads to full sunlight for 5 minutes. The beads will take on their maximum colour at this time. Leave some of the beads exposed to the sun as a reference.
- Place a fabric sample over the beads in open sunlight. Estimate the colour intensity on a scale of 1 to 5 (where 5 represents the colour of the beads in full sunlight and 1 is white) for the fabric sample. If the beads under the fabric remain white, the fabric is blocking the UV radiation.
- Repeat this process for each of the fabric samples.
- Consider the colour intensity of the beads as a function of each of the variables that you used to characterize the fabric samples. Where applicable, plot the colour intensity as a function of the variable. Note any patterns.
- Evaluate your hypothesis in light of your data. If necessary, revise it and conduct more experiments to test it.
Bead colour intensity
Terms/Concepts:UV radiation; UVA, UVB; Spectrum; Fabric properties