Note 4 - Quiz Question The Sun emits a large amount of...

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1 Quiz Question The Sun emits a large amount of power in form of radiation but only a very small fraction of this power warms up the Earth’s surface. This is because A. A large fraction is absorbed on the way from the Sun to the Earth. B. A large fraction is absorbed by the ozone layer surrounding Earth. C. Because the Sun emits in all directions, most of its rays miss the Earth. D. All of the above. Quiz Question The fraction of the Sun’s power that reaches the Earth depends on A. The radius of the Sun B. The radius of the Earth C. The distance between the Sun and the Earth D. A. and B are true E. B. and C are true Introduction • Our system is now the Earth including its atmosphere. • How does a planet lose heat? How is it heated? • What’s the difference between a star and a planet?
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2 Topic 5: Earth Energy Balance • Radiation • Sun’s Radiation • Inverse-Square Law • Sun’s Intensity; • Sun-Earth System • Earth Energy Balance • Seasons Radiation ; Sun’s Radiation; Inverse-Square Law; Sun’s Intensity; Sun-Earth System; Earth Energy Balance; Seasons • In contrast to stars like the Sun, a planet does not have it’s own energy generation from nuclear fusion. • The Earth has a hot iron core and a little radioactivity but this contributes very little to the surface temperature and the climate. • We know that the Earth is surrounded by an atmosphere up to a height of 90 km. Above, there is basically empty space, a very good vacuum. • Only way for Earth to gain or lose heat: Radiation . Radiation ; Sun’s Radiation; Inverse-Square Law; Sun’s Intensity; Sun-Earth System; Earth Energy Balance; Seasons • Incident power, H I , is defined as: • H I = H R + H T + H A • Where: H I = incident power received by the object, • H R = power reflected off the object’s surface, • H T = power transmitted by the object • H A = power absorbed by the object, From www.sensortips.com
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3 Radiation ; Sun’s Radiation; Inverse-Square Law; Sun’s Intensity; Sun-Earth System; Earth Energy Balance; Seasons Radiation; Sun’s Radiation ; Inverse-Square Law; Sun’s Intensity; Sun-Earth System; Earth Energy Balance; Seasons • Fire: Radiates heat in all directions – easy to experience if you walk around it. • The temperature increases as you move closer to the fire. • Similar to a fire or a light bulb, the Sun radiates its energy equally in all directions. Radiation; Sun’s Radiation ; Inverse-Square Law; Sun’s Intensity; Sun-Earth System; Earth Energy Balance; Seasons • Unlike a fire, the Sun consumes its fuel very slowly: On human timescales, the Sun’s surface temperature and power are constant. • If we know the Sun’s radius and its surface temperature,
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Note 4 - Quiz Question The Sun emits a large amount of...

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