Light is a wave of energy, and not all energy wavelengths are visible to the human eye. In this unit, students investigate UV light and chemical reactions and its interesting ability to make certain colors glow or fluoresce. A black light looks dark purple, but most of the light it emits is in the ultraviolet (UV-A) range of the spectrum, which is invisible to the human eye. In this lab, students will investigate the properties of materials.
A phosphor is any substance that absorbs energy and re-emits it as visible light. Under a black light, phosphors convert the UV radiation they receive into visible light. Many natural and man-made materials contain phosphors. When a photon hits a phosphor atom, one of the phosphor's electrons jumps to a higher energy level. This causes the atom to vibrate and create heat. When the electron falls back to its normal level, it releases energy in the form of another photon. This photon has less energy than the original photon, as some energy is lost as heat. In a fluorescent lamp, the emitted light is in the visible spectrum, the phosphor gives off white light we can see. Black lights work on this same principle.
Students will investigate how black light works and build on their understanding of ultraviolet radiation in the electromagnetic spectrum. Laboratory includes table tent cards for phosphor substances and student worksheet. Student worksheet is editable to create a fill-able form that an be used digitally.