The sun's energy output is a maximum in the visible region of the spectrum. One biological reason we might expect or predict this fact is that
A) it would be impossible for biological photosynthesis to occur if any other region dominated the solar spectrum, and thus plant life could not exist on Earth.
B) the visible region comes right in the middle of the overall electromagnetic spectrum.
C) visible radiation is the only type of solar radiation with enough energy to actually burn our skin.
D) the human eye would be expected to evolve in such a way as to make use of the sun's main energy output.
E) the visible region has the highest frequency.
D
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Just as a low-mass main sequence star runs out of fuel in its core, it actually becomes brighter. How is this possible?
A) Helium fusion gives more energy than hydrogen fusion does, based on masses. B) Its outer envelope is stripped away and we see the brilliant core. C) The core contracts, raising the temperature and increasing the size of the region of hydrogen shell-burning. D) It explodes. E) It immediately starts to fuse helium.
The highest-temperature aircraft gas-turbine blades are made from
(a) Tungsten (b) Single crystals of nickel-based alloys (c) Polycrystals of nickel-based alloys (d) Alumina
The first hint that the universe might be expanding came from Vesto Slipher's work with the spectra of spiral nebulae in 1912
Indicate whether the statement is true or false
In a fairly young star cluster, if the most massive stars are swelling up into giants, the least massive stars are:
A) also evolving off the main sequence as well. B) continuing to shine as stable main sequence stars. C) blowing off shells as planetary nebula instead. D) collapsing directly to white dwarfs. E) still evolving toward their ZAMS positions.