The filament in a light bulb has a diameter of 0.050 mm and an emissivity e = 1.0
The temperature of the filament is 3000°C. How long should the filament be in order to radiate 60 W of power? The Stefan-Boltzmann constant is 5.67 x 10-8 W/(m2•K4).
A) 11 cm
B) 9.4 cm
C) 8.6 cm
D) 7.2 cm
E) 5.9 cm
E
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How have supernovae affected the development of life on Earth?
What will be an ideal response?
Interstellar gas is composed of:
A) only hydrogen. B) 90% hydrogen, 9% helium by weight. C) 10% hydrogen, 90% helium by numbers of atoms. D) some hydrogen, but mainly carbon dioxide. E) ammonia, methane, and water vapor.
From a latitude of 60 degrees north during the winter, the Sun will
A) spend most of each day below the horizon. B) spend most of each day above the horizon. C) never be seen above the horizon. D) end a few weeks continuously below the horizon.
An object is placed a distance d from a converging lens. The object is then moved to a distance 2d from the converging lens. Which of the following statements is false?
a. The image in the second case with the object at distance 2d can be the larger one. b. If both images are real, the image in the second case is smaller. c. If the image in the first case is real, the image in the second case is upright. d. The image in the first case with the object at distance d can be the larger one.