CIV300 Test 1 Solutions to Post -Fall 2013(2)

4 marks step 1 total energy output from star above

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Unformatted text preview: by our atmosphere’s gases e.g. CO2, water vapour Two of which could be: • light reflected directly back from ice/snow/high albedo surface • Heat reflected back to space from the tops of clouds • Heat radiated back to space from clouds • Heat radiated back to space from greenhouse gases 2. A distant star of radius 100 million km has a surface temperature of 3,000K. Calculate its energy generated per m2 of surface area. Using the Stefan Boltzmann equation, E = σT4 = 5.67 x 10-8 x (3000)4 = 4.59 x 106W or equivalent in kW. If a planet of radius 5,000km without an atmosphere is orbiting at a distance of 1 billion km from the star, what is the average energy intensity that will fall onto the planet per m2 of its surface area? (4 marks) Step 1 Total energy output from star = Above answer x star’s surface area = 4.59 x 106W x 4x pi x (100x109)2 = 5.77x1029 W/m2 Step 2 At our orbit, this amount is spread thinly over a sphere equal to the orbit. Energy intensity at that orbit is: = 5.77x1029 W/m2 / 4x pi x r2 where r is the planet’s orbit = 5.77x...
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