What is Hubble's law?
A) The longer the time period between peaks in brightness, the greater the luminosity of the Cepheid variable star.
B) The recession velocity of a galaxy is directly proportional to its distance from us.
C) The recession velocity of a galaxy is inversely proportional to its distance from us.
D) The faster a spiral galaxy's rotation speed, the more luminous it is.
E) The faster a spiral galaxy's rotation speed, the less luminous it is.
B
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In a He-Ne laser, the actual emission line at 632.8 nm comes from a jump down in what atom(s)?
A) neon B) helium C) helium and neon D) oxygen E) hydrogen
A velocity selector uses a fixed electric field of magnitude E and the magnetic field is varied to select particles of various energies. If a magnetic field of magnitude B is used to select a particle of a certain energy and mass, what magnitude of magnetic field is needed to select a particle of equal mass but twice the energy?
a. 0.50 B b. 1.4 B c. 2.0 B d. 0.71 B e. 1.7 B
The Cenozoic era consists of only two periods: the ______________ and the Quaternary
Fill in the blank(s) with correct word
Studies have shown that the ice located in the south pole of Mars is mostly ____
a. H2O b. NO2 c. CO2 d. O2 e. FeO2