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Unformatted text preview: Solutions to sample problems for test # 3 1) What is the peak monochromatic radiance from an object (blackbody) in this room at 25 o C? This is a twostep problem. First it is necessary to determine the wavelength at which the radiance is greatest, then the radiance can be calculated for that wavelength. sr m m W m m s J W s m m K J s m m e m s J L K m s J T k hc e hc L m K K m T T k hc µ µ µ µ λ λ µ µ α λ λ 2 6 56 . 9 ) )( 1 ( ) 10 73 . 9 ( ) ( ) 10 . 3 )( 10 63 . 6 ( 2 971 . 4 ) 298 )( 10 73 . 9 )( 10 38 . 1 ( ) 10 . 3 )( 10 63 . 6 ( ) 1 ( 2 73 . 9 298 2898 10 971 . 4 5 6 / 2 8 34 * 73 . 9 6 23 8 34 5 2 * 73 . 9 max = − × × × = = × × × × = − = = = = − − − − − 2) The ocean has an albedo (reflectivity) of about 0.1. What is the irradiance of the ocean if its temperature is 15 o C? 2 4 2 351 ) 288 )( 10 67 . 5 )( 1 . 1 ( ) 1 ( ) ' ( 4 8 4 4 4 * m W K m W K T r Law s Kirchhoff T a T E E = × − = − = = = = − σ σ εσ ε 3) If the sun were twice as large as it is now, but still emitted the same amount of radiant energy, would the irradiance at the top of the Earth’s atmosphere be smaller, larger, or the same as it is now? The simple answer is that the irradiance would stay the same. The radiant energy emitted by the sun will be “spread” out over the surface area of a sphere with radius equal to the distance between the earth and sun. As long as the radiant energy remains the same, so would the irradiance at the top of the atmosphere. 4) If the intensity of a laser decreases by 30% after traveling 1 km in the atmosphere, how much will the intensity have decreased after traveling first 100 m? much will the intensity have decreased after traveling first 100 m?...
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This homework help was uploaded on 04/02/2008 for the course ATMO 446 taught by Professor Brooks during the Spring '07 term at Texas A&M.
 Spring '07
 Brooks

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