Solar spectrum peak: Around which wavelength does the Sun’s radiation reach its maximum intensity (as received at Earth)?

Introduction / Context:
Understanding where the solar spectrum peaks is fundamental in remote sensing, photovoltaic design, and human vision considerations. The Sun approximates a blackbody emitter near 5770 K, so its spectral irradiance peaks in the visible range near green light.

Given Data / Assumptions:

• Solar effective temperature ≈ 5770 K.
• Peak intensity reference is the shortwave spectrum at top of atmosphere, with atmospheric effects only slightly shifting ground measurements.
• Units: micrometre (μm).

Concept / Approach:
By Wien’s displacement principle, the peak wavelength is λ_max ≈ 2898 μm·K / T. For T ≈ 5770 K, λ_max ≈ 0.50 μm. Accounting for actual solar spectrum and common textbook rounding, many references cite ≈ 0.55 μm (green). Remote-sensing bands and camera sensors are aligned with this visible peak for maximal signal.

Step-by-Step Solution:
Estimate λ_max using λ_max = 2898 / 5770 ≈ 0.50 μm.Recognize practical peak in extraterrestrial/atmospheric curves appears around 0.50–0.55 μm.Select the standard rounded value 0.55 μm as the best choice.Reject alternatives at 0.40 μm (violet) and 0.70 μm (red) as off-peak.

Verification / Alternative check:
Solar irradiance standards (AM0/AM1.5) show maximum visible-region energy around green wavelengths, consistent with the 0.5–0.55 μm range.

Why Other Options Are Wrong:
0.40 μm: Too short (near violet); intensity is lower than at green.0.70 μm: Too long (red); descending limb of solar curve.1.00 μm: Near-infrared; below the visible peak.None of these: Incorrect since 0.55 μm is appropriate.

Common Pitfalls:
Confusing human eye sensitivity peak with physical solar peak; fortunately both are close in the green region, aiding daylight vision efficiency.

Final Answer:
0.55 μm.