A Fresnel lens is a type of compact lens that can focus light much like a traditional lens but is thinner and lighter. It consists of a series of concentric grooves, which allow it to bend light efficiently. This design makes it ideal for applications where space and weight are important, such as in lighthouses and projectors. Fresnel lenses are also used in various optical devices, including cameras and solar panels. Their ability to concentrate light makes them useful in enhancing visibility and improving energy efficiency. Overall, they are a significant advancement in lens technology.