The Beurer IL 50 infrared lamp works with IR-A radiation, although this specific detail is not explicitly mentioned in the provided sources, it is common for infrared lamps used for therapeutic purposes, such as muscle relaxation and cold treatment, to utilize IR-A radiation due to its deeper penetration into tissue.

To confirm, IR-A radiation is typically used in medical and therapeutic infrared lamps because it penetrates deeper into the body, providing more effective heat treatment for muscles and other tissues.