The type of electromagnetic spectrum wave with the highest energy is gamma rays. These waves have the shortest wavelengths and the highest frequencies, translating to a significant amount of energy. Gamma rays are produced during nuclear reactions, decay of radioactive materials, and certain astronomical events like supernovae. Their high energy allows them to penetrate many materials, making them valuable in various fields, including medical imaging and cancer treatment. However, their high energy also poses risks, as exposure can damage biological cells.