It takes light about 500 s to reach the Earth from the Sun.

PHYSICS · Multi-part · IB Diploma Programme · Physics · The greenhouse effect · The greenhouse effect

Problem

It takes light about 500 s to reach the Earth from the Sun. (1) a** Determine the average radius of the Earth's orbit around the Sun. (The speed of light is 3×108 ms−13 \times 10^8 \text{ ms}^{-1} ). (2) b** If the Sun's luminosity is L⊙=3.83×1026 WL_{\odot} = 3.83 \times 10^{26} \text{ W}, show that the solar constant, SS, for the Earth is about 1.4 kWm−21.4 \text{ kWm}^{-2}. (3) c** The average solar power per unit area received by the Earth is only 14\frac{1}{4} of this value. Suggest a reason for this. (4) d** The average solar power per unit area incident on the Earth's surface is about 245 Wm−2245 \text{ Wm}^{-2}. Suggest why this value is less than 14\frac{1}{4} of 1.4 kWm−21.4 \text{ kWm}^{-2}.

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