What is the average value of the magnitude of the Poynting vector at 1 meter from a 100-watt lightbulb radiating in all directions?
a. 1 W/m2
b. 4 W/m2
c. 2 W/m2
d. 8 W/m2
e. 12 W/m2
d
You might also like to view...
Each of the following is a prediction of the theory of relativity. Which one is crucial to understanding how the Sun provides light and heat to Earth?
A) If you observe someone moving by you, you'll see their time running slowly. B) Gravity is curvature of spacetime. C) E = mc2 D) Time runs slower on the surface of the Sun than on Earth. E) Space is different for different observers. Time is different for different observers. Spacetime is the same for everyone.
Which is more common: a star blows up as a supernova, or a star forms a planetary nebula/white dwarf system?
A) Supernovae are more common. B) Planetary nebula formation is more common. C) They both occur in about equal numbers. D) It is impossible to say.
The predominant gas in the atmosphere of Venus is
A) oxygen. B) nitrogen. C) water vapor. D) carbon dioxide. E) methane.
The monthly (30 days) electric bill included the cost of running a central air-conditioning unit for 2 hr/day at 5000. W, and a series connection of ten 60. W lightbulbs for 5 hr/day
How much did these items contribute to the cost of the monthly electric bill if electricity costs 8ยข per kW-h?