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physics7c-fall00-mt2-Lee-exam

# physics7c-fall00-mt2-Lee-exam - Physics 7C Fall 2000...

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Physics 7C, Fall 2000, Section 1 Instructor: Adrian Lee Second Midterm Examination, Monday November 6 Name:________________________________________ Student ID:____________________________________ Discussion Section Number/Time/TA:____________________________________ Please write on the paper provided. You can write on both sides of the page. You may use one 8.5" x 11" sheet of double-sided notes. Score _________________________________ Problem 1 (40 pts) _________________________________ Problem 2 (40 pts) _________________________________ Problem 3 (40 pts) _________________________________ Total

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1) The Earth has radius R and is orbiting the Sun at radius r. Ignore the effect of the atmosphere (greenhouse effect) and assume that the Sun and earth have emissivity = 1. a) Show that the surface temperature of the Earth is given by T 4 = P Sun 16 π σ r 2 where P Sun is the radiant power output of the Sun. (25 pts) b) Evaluate the temperature numerically. Use T Sun = 5500K, R Sun = 7 x 10 8 m, σ = 5.7 x 10 -8 W/(m 2 K 4 ), R = 6.4 x 10 6 m, r = 1.5 x 10 11 m. Do you conclude that the atmosphere term is important? (15 pts)
2) Consider an electron with a kinetic energy of 1 keV. The rest mass of an electron is 511 keV/c 2 .

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