Why do some igneous rocks have small crystals?
What will be an ideal response?
If the magma cools quickly, there will be small crystals
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Dry air has a density of 1.29 kg/m3 . What would be the volume of a metric ton of air?
What is the main sequence?
A. a region of cool, luminous stars in the upper right corner of the H-R diagram B. a region of hot dim stars in the lower left corner of the H-R diagram C. the order in which spectral types are listed D. an approximately straight line on the H-R diagram along which 90% of stars lay
The pascal is a pressure unit equal to
A) 1 newton per square meter. B) 1 kilogram per square meter. C) 1 newton per square centimeter. D) 1 kilogram per square centimeter.
Quasar spectra often show many absorption lines that all appear to be due to the same electron transition (such as level 1 to level 2 in hydrogen) but that fall at different wavelengths in the spectrum. Why do we think this is the case?
A) We are seeing absorption lines from clouds of gas that lie between us and the quasar, and therefore each cloud has a different redshift. B) Quasars are rotating rapidly, and this rotation produces spectral lines with a wide variety of Doppler shifts. C) The lines fall at different wavelengths because they are produced by different chemical elements. D) No one knows—it remains perhaps the greatest mystery about quasars.