Ultraviolet-sensitive beads change color when exposed to ultraviolet (UV) light. Students can use these beads to perform inquiry-based experiments to determine if a light source emits UV light or if different materials are able to block it. Students can also use the beads to track their sun exposure.
UV light is a type of electromagnetic radiation with a wavelength shorter than that of visible light, but longer than that of X-rays. The wavelength of UV light ranges between 400 and 10 nm (see Fig. 1). The frequency of UV light is greater than the frequency of violet light in the visible light spectrum. Humans can’t see UV light, but some other organisms are able to perceive it. UV light is a component of sunlight. It is also emitted by mercury lamps, black lights, and the electrons of certain atoms when they have been excited and return to their ground state.
The following inquiry-based activities enable students to investigate UV light using UV-sensitive beads. You have the option of assigning the activities together or independently.
Exploring UV Beads
- Provide students with UV beads and have them expose the beads to UV light to demonstrate that the beads will change color in the presence of ultraviolet radiation.
- Have students working in small groups form a hypothesis as to what environmental changes allow the beads to change color (i.e., detect UV radiation) and what conditions might prevent such a change (i.e., block UV radiation)
- Provide student groups with the means to test their hypotheses by altering the environmental conditions around their beads. Conditions and experiment possibilities include:
- Light source: Compare the effects of sunlight, a UV lamp, an incandescent bulb, and light filtered through colored theatrical film.
- Darkness: Place the beads in a shoebox under a UV lamp.
- Moisture: Dip the beads in water.
- Heat: Place the beads on a heating pad or other warm surface.
- Cold: Place the beads on an ice pack or in ice water.
Wearable UV sensor
- Solar Energy Beads (item #956209)
- Have students decide if they want to make a bracelet, zipper pull, or other type of wearable jewelry.
- Have students cut a piece of ribbon an appropriate length for the piece of jewelry they wish to construct.
- Provide each student with 5 to 10 UV beads to string onto the piece of ribbon and fashion into a bracelet or other design.
- Have students wear the beads for the next week, keeping a journal about when, where, and for how long they are exposed to UV light.
- Have students report their findings to the class, and discuss any results that surprised them. Students may be unaware that they are regularly exposed to UV light, for example, while riding in a car or sitting near a window.