Why is the temperature at the region of a sunspot cooler than the photosphere?
a. They are holes in the photosphere that reveal the lower temperature gases in the deeper layers.
b. They represent points where streams of cool gas from the corona lower the temperature in those regions of the photosphere.
c. Powerful magnetic fields in the sunspots act upon the atoms of the photosphere to prevent them from emitting light.
d. Powerful magnetic fields inhibit the convective flow of the gases of the photosphere downward, allowing them to cool for longer than would normally be permitted.
d
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Two parallel plates of infinite extent perpendicular to the page are situated relative to each other as shown in the figure. The upper plate is at 300°C and the lower plate is at 100°C. Determine the net rate of radiation heat transfer from the upper and lower plate assuming the environment is at a temperature below 100°C. Assume that both the lower surface of the upper plate and the upper surface of the lower plate are black.
GIVEN • The planet Mars revolving around the sun • Diameter of Mars (Dm) = 6600 km • Distance from the sun (Rms) = 225 × 106 km • Diameter of the sun (Ds) =1,384,000 km FIND (a) The equilibrium temperature of Mars (Tm) (b) Tm assuming that the albedo of Mars = 0.15 ASSUMPTIONS • Both Mars and the sun act as blackbodies • The sun has an equivalent blackbody temperature (Ts) of 5600 K PROPERTIES AND CONSTANTS The Stephan-Boltzmann constant (?) = 5.67 × 10–8 W/(m2 K4)
The least important power of a telescope is _____
A) magnifying power B) light-gathering power C) resolving power D) reflecting power
Energy in Capacitors: When a 4-?F capacitor has a potential drop of 20 V across its plates, how much electric potential energy is stored in this capacitor?
A. 0.8 ?J B. 8 ?J C. 80 ?J D. 800 ?J E. 8000 ?J
Which statement about the Moon's solar month and sidereal month is correct?
A. The solar month is the same length as the sidereal month. B. The solar month is more than two days longer than the sidereal month. C. The solar month is more than two days shorter than the sidereal month. D. The solar month is used in our calendars during the summer season while the sidereal month is used only during the winter season.