Consider a light bulb, in empty space, radiating 200. watts with its filament heated to 2800.°C. Assuming it is a good approximation to a black body
(a) What is the area of the filament?
(b) If placed in an oven, with walls at 800.°C, what is its net power radiated now?
(a) 39.6 mm2
(b) 197. watts
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The lunar maria are
a. the lava plains of the lunar lowlands. b. the smooth plateaus of the lunar highlands. c. less than one billion years old. d. moving plates of lunar crust. e. older than the lunar highlands.
The sum of orthogonal vectors V1 and V2 is (4i 2 8j 1 7k). A unit vector along V1 is (0.635i 1 0.773j). Vector V1 is:
(A) 0.635i 1 0.773j (B) 21.635i 1 2.773j (C) 22.35i 22.82j (D) 2.57i – 1.73j
Which is heaviest?
A) oxygen atom B) hydrogen atom C) electron D) proton E) water molecule
Calculate the pressure amplitude (in N/m2) of a 500 Hz sound wave in helium if the displacement amplitude is equal to 5.0 × 10^-8 m. (r = 0.179 kg/m3, v = 972 m/s.)
a. 3.5 × 10^-2 b. 1.6 × 10^-2 c. 2.7 × 10^-2 d. 4.2 × 10^-2 e. 2.0 × 10^-2