Sun's blackbody radiation distributes most total energy in infrared

Steps:

• Recall the Sun approximates a blackbody at ~5800 K, following Planck's law for spectral radiance.
• Apply Wien's displacement law: peak wavelength λ_max ≈ 500 nm (visible light), but total energy integrates across spectrum.
• Note the blackbody curve's asymmetry: ~50% energy shortward of peak (UV/visible), ~50% longward (infrared), with infrared band (0.7–1000 μm) capturing the majority.
• Compare bands: infrared holds ~49% of total output, exceeding visible (~44%) and far outpacing others.

Why A is correct:

• Infrared encompasses the broad tail of the spectrum where most integrated energy lies, per blackbody energy distribution.

Why the others are wrong:

• B: Microwaves are much longer wavelengths; negligible Sun emission there.
• C: Radio waves even longer; Sun's radio output is minimal compared to optical/IR.
• D: X-rays are high-energy, short-wavelength; Sun emits little due to moderate temperature.

Final answer: A