Where are the X-rays produced that are emitted by quasars and other active galactic nuclei?
A) in the hot gas in an accretion disk around a central black hole
B) in dust grains in molecular clouds that encircle the active galactic nucleus
C) in an ionization nebulae of interstellar gas surrounding the accretion disk
D) in fast-moving jets of electrons that are ejected from the active galactic nucleus
E) all of the above
A
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In an n-type semiconductor, the conduction-band energy is 1.1 eV and the donor energy level is 1.0 eV. At temperatures approaching 0 K the Fermi energy is equal to:
(a) 1.1 eV (b) 1.0 eV (c) 1.05 eV (d) 0.55 eV
The iron we commonly find in our surroundings came from
A) the iron core of a massive star which exploded as a type I supernova. B) planetary nebulae. C) jets ejected by a rapidly spinning pulsar. D) material ejected by a nova explosion. E) decay of nickel 56 and cobalt 56 in a supernova remnant.
What is the longest wavelength in the Lyman Series?
A) 45.60 nm B) 91.20 nm C) 121.5 nm D) 240.1 nm E) 365 nm
A ceiling fan is turned on and reaches an angular speed of 120 rev/min in 20 s. It is then turned off and coasts to a stop in an additional 60 s. The ratio of the average angular acceleration for the first 20 s to that for the last 60 s is which of the following?
a. 3 c. 0.3 b. –3 d. –0.3