IB Physics SL B 2 6 Mean Solar Intensity Questions

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 incoming solar intensity as S/4 by comparing the planet’s projected disc area with its total surface area.
Calculate global mean absorbed intensity by applying atmospheric transmission or planetary albedo to mean incoming solar intensity.
Use mean absorbed solar intensity and emissivity to calculate a planet’s equilibrium surface temperature.

[Maximum number: 2]

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

Figure for Question IB Physics SL B 2 6 Mean Solar Intensity Questions 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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IB Physics SL B 2 6 Mean Solar Intensity Questions question 1