A radiometer has two square vanes (each measuring 1.0 cm by 1.0 cm), attached to a light horizontal cross arm, and pivoted about a vertical axis through the center, as shown in the figure.
The center of each vane is 6.0 cm from the axis. One vane is silvered and it reflects all radiant energy incident upon it. The other vane is blackened and it absorbs all incident radiant energy. An electromagnetic wave with an intensity of 0.30 kW/m2 is incident normally upon the vanes. What is the electromagnetic power absorbed by the blackened vane? (c = 3.00 108 m/s,
0 = 4 10-7 T m/A, 0 = 8.85 10-12 C2/N m2)
A) 0.030 W
B) 0.040 W
C) 0.050 W
D) 0.060 W
E) 0.090 W
Question 2
Near the earth the intensity of radiation from the sun is 1.35 kW/m2. What volume of space in this region contains 1.0 J of electromagnetic energy? (c = 3.0 108 m/s, 0 = 4 10-7 T m/A, 0 = 8.85 10-12 C2/N m2)
A) 4.5 10-6 m3
B) 3300 m3
C) 7.4 10-4 m3
D) 1400 m3
E) 220,000 m3
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