In order for the atoms in a neon discharge tube (or a neon beer sign) to emit their characteristic orange light, it is necessary that
A) there be no unoccupied energy levels in each atom.
B) each atom carry a net electric charge.
C) the atoms be continually replaced with fresh atoms, because the energy of the atoms tends to be used up with continued excitation, resulting in dimmer and dimmer light.
D) electrons first be given energy to raise them from their ground state to an excited state.
D
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Spectroscopic and eclipse duration observations of an eclipsing binary star can enable astronomers to calculate________ of its individual stars
a. the masses b. the sizes c. the masses and sizes d. neither masses nor sizes
Most galaxies in the Local Group are
A) dwarf spirals. B) small irregulars similar to the Magellanic Clouds. C) larger spirals than either the Milky Way or M-31 in Andromeda. D) dwarf ellipticals, similar to the companions of M-31. E) brown dwarfs, with even more dust than our own Galaxy.
In noting that our world is "differentiated," we mean that
A) the density of its materials decreases as you go downward toward the core. B) the Earth has evolved in a different pattern than any other planet. C) the iron and nickel core is denser than the silicate mantle and crust. D) radioactive heating in the core is at a slower pace than when the Earth was new. E) the Earth's magnetic field is different now in polarity than it was 700,000 years ago.
According to Heisenberg's uncertainty principle, the more we know about a particle's momentum, the less we know about its
A) kinetic energy. B) mass. C) speed. D) location. E) none of the above