The presence of ozone in the stratosphere is responsible for
(1) increasing the average global temperature in recent years
(2) higher rate of photosynthesis
(3) checking the penetration of ultra-violet rays to the Earth
(4) supplying oxygen for people traveling in jets
Answer: (3) 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 the 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). The small unabsorbed part that remains of UV-B after passage through ozone causes sunburn in humans and direct DNA damage in living tissues in both plants and animals.
