A radiometer is a scientific instrument designed to measure the intensity of electromagnetic radiation, particularly in the form of light. It typically consists of a set of vanes mounted on a spindle, which rotate when exposed to light. The movement of the vanes helps scientists understand the energy and intensity of the radiation being measured. Radiometers are often used in various fields, including meteorology, astronomy, and environmental science. They can help researchers study the effects of sunlight on the Earth's atmosphere, monitor solar energy, and analyze the properties of different light sources.