The unified model describes active galactic nuclei using
a. a super massive black hole at the center of a normal spiral galaxy.
b. a super massive black hole surrounded by an accretion disk and dense disk of gas.
c. an accretion disk around a neutron star.
d. gravitational lenses to intensify the radiation coming from them.
e. different lines of sight toward and dwarf irregular galaxy.
B
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Spectral Series: The Paschen series is formed by electron transitions that
A. end on the n = 1 shell. B. begin on the n = 1 shell. C. end on the n = 2 shell. D. begin on the n = 3 shell. E. end on the n = 3 shell.
Calculate the pressure exerted on the ground due to person standing on one foot if the bottom of the person's foot is wide and long
A) 2.1 × 104 Pa B) 2.2 × 103 Pa C) 4.8 × 104 Pa D) 5.3 × 104 Pa
Why is continental crust lower in density than seafloor crust?
A) Continental crust is made of rock, while seafloor crust has more metals. B) Continental crust is made from volcanic rock called basalt, which is lower in density than what the seafloor crust is made from. C) Continental crust is made from remelted seafloor crust and therefore only the lower-density material rises to form it. D) Continental crust is actually denser than seafloor crust. E) Seafloor crust is more compact due to the weight of the oceans, but it is made of the same material as the continental crust.
Saturn's icy moon Enceladus
A) has an ancient, heavily cratered surface reminiscent of the Moon B) is small and irregular in shape like an asteroid C) has a smooth, icy surface criss-crossed with dark cracks D) has fountains of ice particles and water vapor spraying out from its surface