(a) Explain the concept of the effective (radiation) temperature of a planet. 3]
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Question
(a) Explain the concept of the effective (radiation) temperature of a planet. 3] (b) Venus has a radius of 6050 km, orbits the Sun at a distance of 1.08 x 108 km and has an albedo of 0.78. Calculate the effective temperature of Venus. Given that the Sun has a surface temperature of 5770 K and a radius of 6.96 x 10 km [3 (c) The actual surface temperature of Venus is 740 K. Briefly explaining this ob- servation using the principles of different transmittance of the atmosphere for 3 short-wave photons and long-wave photon. A diagram may be useful.Explanation / Answer
a. Effective temperature: The effective temperature of planet is the temperature which emits the same ammount of electromagnatic radiation. This is used as surface temperature of a planet. The effective(radiation) temperature of a planet can be calculated by energy balance which comes in the earth equating which goes out from the earth.
If we look at the earth , the effective temperature differs according to the climate and earth surface. Emitted radiation equals to a constant times and as the earth is a fast rotator planet,thus the ratio of the area estimates as 1/4th. The effective radiating temperature is expressed in Kelvins.
Radiation emitted by the Earth = constant x T4
(with the constant = 5.67 x 10-8 W /m2/K4)
By this equation we can know that how much energy the Earth receives and how much radiation is emitted. Using this energy balance calculation we can easily get the amount of temperature equating What comes and what goes out.
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