Stratospheric protection: Harmful ultraviolet radiation from the sun is largely absorbed by which atmospheric layer or constituent high above the earth surface?

Introduction:
Incoming solar radiation spans ultraviolet, visible, and infrared wavelengths. Ultraviolet radiation at shorter wavelengths can damage biological tissues and DNA. Earth enjoys natural protection due to a specific atmospheric constituent concentrated in the stratosphere known as the ozone layer.

Given Data / Assumptions:

• Reference to high altitude absorption.
• Concern is harmful ultraviolet band.
• Focus on the dominant absorber for UVB and part of UVC reaching the upper atmosphere.

Concept / Approach:
Ozone, represented as O3, exhibits strong absorption bands in the ultraviolet region. Stratospheric ozone between roughly 15 km and 35 km altitude forms the ozone layer that filters much of the UVB and nearly all UVC before it reaches the surface. Variations in ozone concentration affect the amount of UV reaching the ground and thereby influence health and ecosystems.

Step-by-Step Solution:
Identify the absorber for UV: ozone molecules in the stratosphere.Clarify altitude: high above the troposphere, in the stratosphere, not a generic gas layer.Confirm that CO2 primarily affects infrared absorption and climate, not UV shielding.Therefore the correct answer is the ozone layer.

Verification / Alternative check:
Measurements of total column ozone and the ozone hole in polar regions correlate with surface UV index, confirming its shielding role.

Why Other Options Are Wrong:
Hydrogen and argon layers are not meaningful UV shields. Carbon dioxide absorbs in infrared bands. None of these is incorrect because ozone is the specific absorber.

Common Pitfalls:
Confusing greenhouse gas effects with UV protection. Greenhouse gases trap heat but do not provide the UV shielding function of ozone.

Final Answer:
Ozone layer