A radiometer has two square vanes (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 torque due to radiation pressure on the vane assembly about the vertical axis?
(c = 3.00 × 108 m/s, ?0 = 4? × 10-7 T ? m/A, ?0 = 8.85 × 10-12 C2/N ? m2)
A) 2.4 × 10-12 N ? m
B) 6.0 × 10-12 N ? m
C) 1.2 × 10-11 N ? m
D) 1.8 × 10-11 N ? m
E) 2.4 × 10-11 N ? m
Answer: B
You might also like to view...
You're driving in a car at 50 km/h and bump into a car ahead traveling at 48 km/h in the same direction. The speed of impact is
A) zero. B) 2 km/h. C) 48 km/h. D) 50 km/h. E) 98 km/h.
The Galactic Year is the time for our solar system to orbit the Galaxy; it is about
A) 15 million years. B) 225 million years. C) 4.5 billion years. D) 9.6 billion years. E) 13.5 billion years.
Energy Levels: A hydrogen atom is excited to the n = 9 level. Its decay to the n = 6 level detected in a photographic plate. What is the frequency of the light photographed? (1 eV = 1.60 × 10-19 J, h = 6.626 × 10-34 J ? s)
A. 5.08 × 1013 Hz B. 5910 Hz C. 5910 nm D. 3.28 × 10-9 km
A vertically-held sledge hammer is easier to balance when the heavier end is
A) on your hand. B) at the top, away from your hand. C) the same either way