Home › PYQs › Environment › All questions › 1986 · Ozone layer
UPSC Prelims 1986 · Environment · Pollution Files
Which of the following statements about ozone layer is correct?
- (a) It converts UV radiations into electrical energy
- (b) It protects the earth's life forms by preventing the damaging UV radiations from reaching earth's surface
- (c) It is of uniform thickness
- (d) None of the above
Show the answer and explanation
Answer: (b) It protects the earth's life forms by preventing the damaging UV radiations from reaching earth's surface
It stops most damaging UV from reaching the surface.
The idea
The ozone “layer” is not a sheet. It is a region of the stratosphere where ozone is a little more concentrated. If all of it were brought down to sea-level pressure it would be only about 3 mm thick. That thin shield stops most of the damaging ultraviolet.
Most ozone is made over the tropics, where sunlight is strongest → Stratospheric winds carry it towards the poles → So the layer is thinner over the tropics and thicker at higher latitudes → It also changes with season
Why the others are wrong
(a) Ozone doesn’t make electricity.
(c) Its thickness varies with latitude and season (thinnest at the tropics; the Antarctic hole each spring).
Also know
Thickness is measured in Dobson units: 100 units equal 1 mm at sea-level pressure, and the world average is about 300. An area below 220 units is called an ozone hole.
🔒 Ozone is measured in Dobson Units (~300 DU normal; hole = below 220 DU).