Unformatted text preview: Physics 1353 Quiz #ZD Key Spring 2008
Instructions: Write your name on the back oft/us Sheet & do your work on thefront. 1. At a certain point in space, at a certain instant of time, the magnetic ﬁeld of a light wave points in the — x — direction and is given by Bx = ~ B”, cos(kz + wt). In L
which direction does the wave travel? In which direction does the associated / ﬁll x
electric ﬁeld point? (2 pts.) ‘ A/i
Direction wave travels: E Direction of E: 2. The Earth (radius 6.4 X 106 m) orbits the Sun (power 3.83 X 1026 J/s) in a (roughly) circular orbit of radius
1.5 X 10H m. Assuming that the Earth absorbs 65% of the incident solar radiation and reﬂects 35%, What force
does the Sun’s radiation exert on the Earth? Be sure to include units with your answer. (8 pts) P 3.83>< 10%; . M. . ,
I I 2 == "H—m—é‘j = l.35>< 103 v27 = intensrty of sunlight at Earth
4”Res 47r(1.5>< 10” m) "'
(0.651)A (0.351) A IA 7 A. .
rad — C + 2 C — (1.35)? Where A = ERE‘: harth cross—sectional area
(1.35)(1.35 >< 10315;)“64 X 106 my
Fm _ 8 _ 7.8x 108 N
" 3.00>< 10 m/ 8 Force of Radiation on Earth = 7.8 X 103 N ...
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 Spring '08
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