UV-B is ionizing radiation in the range of 250-320 nm. Exposure of the naked skin results in rapid reddening and sunburn. Solar radiation only has a small portion of UV-B.
Sunscreen lotions are formulated to block out the UV-B portion (look up SPF testing – Labsphere UV-2000S).
UV-B is produced artificially by UV-B lamps, which are either fluorescent or halogen type.
UV-B radiation is used for therapeutic exposure under medical supervision (e.g. Psoriasis and similar skin conditions).