A light source comprises light emitting diodes (LED) (1) with a monocrystal (2), covered by a cap (3) of a transparent material at one side and fitted with an anode contact element (4) to supply and a cathode contact element (5) to lead away direct current at the other side. The LED's arranged in a row are connected with their anode contact elements to one thermally and electrically conductive cooling plate (43, 45) and with their cathode contact elements (5) to another cooling plate (53, 55). These mutually insulated cooling plates are arranged with their lateral sides next to each other and on the surfaces averted from the LED's they are fitted with cooling elements for transfer of heat to cooling media. The cooling elements may comprise sets of cooling fins (44, 54; 46, 56) arranged on the sides of the cooling plates averted from the LED's.