Overexposure to certain wavelengths of strong sunlight is the main cause of melanoma, a virulent form of skin cancer  For this reason, doctors now urge everyone to put adequate sunblock on skin exposed to strong sunlight
Adequate sunblock, according to doctors, is any preparation that prevents sunburn even if the person is exposed to strong sunlight for a significant length of time
There is no evidence that there are wavelengths of sunlight that lead to both sunburn and melanoma.