IB Physics SL B.2.6 Mean solar intensity Question Bank

Practise IB Physics SL B.2.6 by deriving global mean solar intensity and using albedo to model absorbed energy and planetary temperature.

Exam points

Derive global mean intensity as S/4 by comparing Earth's intercepting disc with its full surface.
Combine S/4 with albedo and emissivity to calculate absorbed intensity or equilibrium temperature.

[Maximum number: 2]

The diagram shows a simplified energy-balance model for the Earth surface–atmosphere system.

Figure for Question B.2.6—Mean solar intensity question 1 — IB Physics SL

The following data are given:

\begin{aligned} \text { Average albedo of Earth } & =0.30 \\ \text { Average global temperature of the surface } & =288 \mathrm{~K} \\ \text { Average Earth-Sun distance } & =1.5 \times 10^{11} \mathrm{~m} \end{aligned}

Show that the average global intensity of radiation absorbed by the surface is about $240 \mathrm{Wm}^{-2}$ .

Average incoming intensity $=\frac{S}{4}$ « $=340 \mathrm{~W} \mathrm{~m}^{-2}$ »

Absorbed intensity $=(1-0.30) \times 340$ or $238 \mathrm{~W} \mathrm{~m}^{-2}$

The steps in the calculation must be
shown.

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B.2.6—Mean solar intensity question 1