(3) checking the penetration of ultra-violet rays to the earth Explanation: Ozone in the ozone layer filters out sunlight wavelengths from about 200 nm UV rays to 315 nm, with ozone peak absorption at about 250 nm. This ozone UV absorption is important to life, since it extends the absorption of UV by ordinary oxygen and nitrogen in air (which absorbs all wavelengths < 200 nm) through the lower UV-C (200 nm-280 nm) and the entire UV-B band (280 nm-315 nm).