Identify a true statement about quasars
A) Their spectra are similar to the spectra of stars.
B) Their spectra do not show any redshift.
C) They exhibit fluctuations in their brightness over time scales of hours or minutes.
D) They are supermassive structures with a diameter of 20 to 50 Mpc.
C
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Which of the following correctly states the number of comets that scientists estimate to be located in the Oort cloud and the number that have actually been observed in the Oort cloud (with telescopes)?
A) estimated number in Oort cloud: 1 trillion observed in Oort cloud: zero B) estimated number in Oort cloud: 1 million observed in Oort cloud: 1,000 C) estimated number in Oort cloud: 100,000 observed in Oort cloud: 50 D) estimated number in Oort cloud: 1 billion observed in Oort cloud: 10,000
Which of the following are candidates for galactic dark matter?
A) faint red stars B) brown dwarfs C) Jupiter-size objects D) WIMPs E) all of the above
Coulomb's Law: Three identical 3.0-µC charges are placed at the vertices of an equilateral triangle that measures 30 cm on a side. What is the magnitude of the electrostatic force on any one of the charges? (k = 1/4??0 = 9.0 × 109 N ? m2/C2)
A. 1.6 N B. 1.8 N C. 2.0 N D. 2.2 N E. 2.4 N
In the quantum model of the atom, the location of the electron is described in terms of ______________
Fill in the blank(s) with correct word