A light source comprises at least one light-emitting component, in particular a component emitting ultraviolet light and/or a semiconductor component, and a line system, through which a cooling fluid can flow in a flow direction, for controlling the temperature of the at least one light-emitting component, and also a first and a second cooling-fluid pressure sensor, which are arranged one after the other in the line system in the flow direction, and an electronics unit which is connected to the first and second cooling-fluid pressure sensors and configured to determine at least one diagnostic, control and/or regulating value on the basis of pressures captured by the first cooling-fluid pressure sensor and by the second cooling-fluid pressure sensor.