'Ozone layer' absorbing ultra-violet radiation exists in which of the atmospheric layer?

Question

UnlockIAS · Accepted Answer

Correct — D, Stratosphere. The ozone layer lies in the lower-to-middle stratosphere, roughly 15-35 km above the surface. There, ozone (O3) absorbs most of the Sun's harmful ultraviolet (UV-B and UV-C) radiation. This absorption also warms the stratosphere, so its temperature rises with height (a temperature inversion). This UV-shielding by stratospheric ozone is what makes complex life on Earth possible.

Why the other options are wrong — (a) The troposphere (0 to about 12 km) is the lowest layer, where weather occurs; the protective ozone layer sits above it in the stratosphere. Ozone at ground level here is a pollutant, not the shielding ozone layer.  (b) The mesosphere (about 50-85 km) lies above the ozone layer and is where meteors burn up; it is not where the ozone layer is concentrated.  (c) The thermosphere (about 85-600 km) contains the ionosphere and auroras; it is far above the stratospheric ozone layer.

Concept: Earth's atmosphere is layered by its temperature profile: troposphere, stratosphere, mesosphere, thermosphere and exosphere. The stratosphere contains the ozone layer, which absorbs solar UV radiation. Because absorbing UV heats it, the stratosphere's temperature increases with altitude — making it stable and cloud-free, which is why jet aircraft prefer to cruise there.

State PCS 2023 Q143 — Geography PYQ with Answer

State PCS 2023 Q143 — Geography PYQ with Answer