If the spectrum of a sunspot shows that it has a maximum intensity at 650 nm, what is the temperature of the sunspot?
a. 650 K
b. 5000 K
c. 1950 K
d. 4500 K
e. 10,000 K
d
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A positively charged electron is
A) called a positron. B) called a muon. C) called a proton. D) not found in nature. E) called a pion.
The tip of a soldering iron consists of a 0.6-cm diameter copper rod, 7.6 cm long. If the tip must be 204°C, what are the required minimum temperature of the base and the heat flow, in watts, into the base? Assume that h= 22.7 W/(m2 K) and Tair = 21°C.
GIVEN
FIND
(a) Minimum temperature of the base (Ts)
(b) Heat flow into the base (q) in W
ASSUMPTIONS
The tip is in steady state
The thermal conductivity of copper is uniform and constant, i.e., not a function of temperature
The copper tip can be treated as a fin
SKETCH
Electrons in a particle beam each have a kinetic energy of 3.2 × 10^-17 J. What is the magnitude of the electric field that will stop these electrons in a distance of 0.05 m? (e = 1.6 × 10^-19 C)
a. 2000 N/C c. 200 N/C b. 4000 N/C d. 1000 N/C
In an ideal case rays coming from an object toward a lens or mirror should be reasonably close to the optical axis. To the extent that this condition is not completely met, which one of the following effects occurs?
a. mirages c. spherical aberration b. chromatic aberration d. light scattering