traviolet (UV) rays are used in our daily lives for a variety of purposes, including detection of counterfeit bank notes and passports, sterilisation in hospitals and water treatment plants, and in medical treatments for diseases such as athlete's foot. However, a majority of students are unaware of UV rays and their effects. This practical introduces students to the different types of UV rays and their effects on living things, using appropriate teaching materials and equipment. The effects of exposure to UV-B (fluorescent) and UV-C (germicidal) lamps are demonstrated using bananas, duckweed and the fruit fly. Students can observe photoreactivation when living samples are exposed to the UV-C followed by irradiation with the UV-B lamp.