Which of these is not involved in the operation of lasers?
a. stimulated emission b. population inversion
c. metastable state d. blackbody radiation
d
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An interstellar gas is emitting 10-centimeter wavelength radiation, and a nearby star is emitting 10-micrometer wavelength radiation. Which of these can you observe through an Earth-based telescope?
A. the star B. the interstellar gas C. both interstellar gas and the star D. None of these choices are correct.
What kinds of objects are found in the Milky Way disk?
A. Blue stars B. Some red stars C. Open clusters D. Gas and dust E. All of the above
Astronomers have found the center of the Universe to be located in
a. Earth b. the Sun c. Sagittarius A d. the Virgo Cluster of galaxies e. no center is thought to exist.
Considering only the role of dark energy and keeping all other factors the same, which hypothetical universe is oldest?
A) the one with more dark energy B) the one with less dark energy C) Dark energy doesn't affect the inferred age of the universe.