SSC CGL 2024 Tier-I · 11 September 2024, Shift 1 · General Awareness · Question 20 of 95

Text as printed on a candidate's response sheet for this shift; answer per SSC's tentative key as marked on that sheet. Solution last reviewed 10 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. The questions and options here are reproduced as printed on a candidate's own response sheet for this shift — the Commission's text, unchanged. Each answer is SSC's tentative key as marked on that sheet; SSC allowed challenges to it and never publishes a final key. The solutions are written by UnlockIAS.

What kind of radiation is absorbed by the ozone layer?

(a)Infrared radiation
(b)Visible radiation
(c)Green radiation
(d)Ultraviolet radiation

Answer

Why

Correct — D. The ozone layer absorbs ultraviolet radiation, which is option (d).

Ozone (O₃) absorbs strongly in the ultraviolet band. It takes out effectively all UV-C and most UV-B, the shortest and most damaging solar ultraviolet, while UV-A largely gets through.

The absorption is not passive. The energy splits O₃ into O₂ and a free oxygen atom, which recombine to make ozone again — a cycle that both destroys and rebuilds the layer while converting the ultraviolet into heat.

Why the others are wrong

(a)
Infrared radiation — Infrared is the band trapped near the surface by greenhouse gases such as water vapour and carbon dioxide. That is the greenhouse effect, a different mechanism at a different altitude from the ozone shield.
(b)
Visible radiation — Visible light passes through the atmosphere almost unimpeded — that transparency is why daylight reaches the ground at all. Ozone does not block it.
(c)
Green radiation — Green radiation is not a band of the electromagnetic spectrum. Green is one colour within visible light, and no atmospheric layer is defined by absorbing a single colour.

Concept

The ozone layer sits in the stratosphere, roughly 15 to 35 km up, where ozone is concentrated enough to act as a filter.

Solar ultraviolet is divided into UV-A, UV-B and UV-C by decreasing wavelength and increasing energy. Ozone removes essentially all UV-C and most UV-B. What reaches the surface is mostly UV-A, which is why ozone depletion is discussed in terms of extra UV-B getting through.

Each layer of the atmosphere absorbs a different band, and that is the distinction the question is really testing.

Key facts

Stratospheric ozone absorbs ultraviolet radiation, blocking essentially all UV-C and most UV-B.
UV-A largely reaches the surface, so ozone depletion is measured by the extra UV-B that gets through.
The ozone layer lies in the stratosphere, roughly 15 to 35 km above the surface.
Absorbing ultraviolet splits ozone into O2 and atomic oxygen, which then recombine.

Study next

The electromagnetic spectrum in order of wavelength and the uses of each bandOzone depletion, chlorofluorocarbons and the Montreal ProtocolLayers of the atmosphere and what each one absorbs

Common traps

Choosing infrared by confusing the ozone shield with the greenhouse effect.
Treating a colour name such as green as a separate kind of radiation.

The spectrum is worked from both ends in this same 11 Sep 2024, 09:00 paper: GA Q.3 asks which radiation has wavelengths under 10⁻³ nm and is produced by nuclear explosions, where the answer is gamma.

Related PYQs

No directly related past PYQ was found.