IBDP Physics- B.2 Greenhouse effect - IB Style Questions For HL Paper 1A -FA 2025

Correct Answer: \( \boxed{\mathrm{B}} \)

Albedo is the fraction of incident radiation that is reflected:

\(\mathrm{albedo}=\frac{I_{\mathrm{reflected}}}{I_{\mathrm{incident}}}\)

For region X,

\(\mathrm{albedo}_X=\frac{150}{500}=0.30\)

For region Y,

\(\mathrm{albedo}_Y=\frac{180}{500}=0.36\)

Therefore, region Y has the greater albedo.

The absorbed intensity is the incident intensity minus the reflected intensity. For X,

\(I_{\mathrm{absorbed},X}=500-150=350\,\mathrm{W\,m^{-2}}\)

For Y,

\(I_{\mathrm{absorbed},Y}=500-180=320\,\mathrm{W\,m^{-2}}\)

Since X and Y have the same surface temperature, the thermal radiation emitted per unit area depends on emissivity according to

\(P=\varepsilon\sigma T^4\)

The radiated intensity is \(350\,\mathrm{W\,m^{-2}}\) for X and \(320\,\mathrm{W\,m^{-2}}\) for Y. Since their temperatures are equal, the region with the greater radiated intensity has the greater emissivity.

Therefore, region X has the greater emissivity.

Thus,

\( \boxed{\text{Greater albedo: Y,\quad Greater emissivity: X}} \)

Hence, the correct answer is \( \boxed{\mathrm{B}} \).