The hydrogen lines in spectral type A stars
a. are most narrow for supergiants.
b. are most narrow for main sequence stars.
c. can not be used to estimate the luminosity of the star.
d. are very weak and difficult to see.
e. are useful in determining the apparent magnitude of the star.
A
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One in 4 600 water molecules contains a deuterium atom. If all the deuterium could be extracted from 1 m3 of water and then reacted, how much energy could be obtained? (Each D-D fusion liberates 3.65 MeV of energy, 1 MeV = 1.6 × 10^–13 J, ?water = 103 kg/m3, one mole of water has a mass of 18 g, and NA = 6.02 × 10^23)
a. 4.2E+12 J b. 1.3E+25 J c. 3.5E+11 J d. 2.1E+12 J e. 6.9E+14 J
Coffee will cool faster when put into a saucer due to
a. conduction b. evaporation c. condensation d. a and b e. b and c
Spherical Mirrors: Tan's face is 20 cm in front of a concave shaving mirror. If he observes his image to be twice as big and upright, what is the focal length of the mirror?
A. 10 cm B. -40 cm C. -50 cm D. 40 cm E. 50 cm
Which was the last part of the planet-forming process?
A. formation of the planetesimals B. formation of the planets' core C. formation of the atmosphere of the planets D. formation of the Sun