Atmospheric absorption: which band of electromagnetic radiation is most effectively absorbed by carbon dioxide (CO2) near the lower boundary of the troposphere?

Introduction / Context:
Greenhouse gases like carbon dioxide play a central role in the Earth’s energy balance by absorbing and re-emitting thermal radiation. Recognizing the spectral bands where CO2 absorbs strongly is fundamental in meteorology, climatology, and remote sensing.

Given Data / Assumptions:

• CO2 absorption bands exist primarily in the thermal infrared.
• Question focuses on the lower troposphere (near-surface atmosphere).
• Solar UV/visible are largely unaffected by CO2 compared with IR bands.

Concept / Approach:
CO2 has strong vibrational transitions in the infrared, notably around 4.3 μm and 15 μm. These bands absorb terrestrial (longwave) radiation emitted by the surface and atmosphere, leading to greenhouse warming effects near the surface.

Step-by-Step Solution:
Identify spectral domain relevant to CO2: thermal IR, not X-ray or UV.Relate to greenhouse mechanism: Earth emits predominantly in IR; CO2 absorbs and re-emits in IR bands.Select infrared as the correct option.

Verification / Alternative check:
Atmospheric transmission curves show strong CO2 absorption near 15 μm, a cornerstone of greenhouse physics.

Why Other Options Are Wrong:

• X-rays/UV are not significantly absorbed by CO2; other species and the upper atmosphere dominate UV absorption.
• Visible light passes through nearly unaffected by CO2.

Common Pitfalls:

• Confusing ozone's UV absorption with CO2's IR absorption.

Final Answer:
Infra-red rays