Of the following photons, which has the lowest energy?
a. visible b. ultraviolet
c. infrared d. microwave
d
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Which of the following describes a primary role of global circulation cells in a planet's atmosphere?
A) They transport heat from the equator toward the poles. B) They create severe weather such as thunderstorms. C) They cause air to be diverted into hurricane-like swirls. D) They keep the poles cold enough to have polar caps.
Motion in a circle at constant speed is motion with
a. constant acceleration. b. constant velocity. c. both of the above d. none of the above
The equivalent capacitance of the circuit shown below is
A. 0.2 C. B. 0.4 C. C. 1 C. D. 4 C. E. 5 C.
For an ideal radiator (hohlraum) with a 10-cm-diameter opening, located in black surroundings at 16°C, (a) calculate the net radiant heat transfer rate for hohlraum temperatures of 100°C and 560°C, (b) the wavelength at which the emission is a maximum, (c) the monochromatic emission at ?max, and (d) the wavelengths at which the monochromatic emission is 1 per cent of the maximum value.
GIVEN
• An ideal radiator (hohlraum) in black surroundings
• Radiator opening diameter (D) = 10 cm = 0.1 m
• Surrounding temperature (Ts) = 16°C = 289 K
• Hohlraum temperatures
- Th1 = 100°C = 373 K
- Th2 = 560°C = 833 K
FIND
(a) The net radiant heat transfer rate (qr)
(b) The wavelength at which the emission is maximum (?max)
(c) The monochromatic emission at ? max (E?max)
(d) The wavelengths at which the monochromatic emission is 1% E?max
SKETCH
PROPERTIES AND CONSTANTS
the Stephan-Boltzmann constant (?) = 5.67 × 10–8 W/(m2 K4)