Explain how observations of white-dwarf supernovae provide information on the expansion of the universe when it was younger
What will be an ideal response?
White-dwarf supernovae attain the same maximum brightness and are therefore good standard candles with which to measure galaxy distances. Therefore, if we see a white-dwarf supernova in a distant galaxy we can measure how far away it is, and thus how old the universe was when the supernova exploded. We can also measure the Doppler shift of spectral lines in the galaxy and find how fast it is moving away from us. This tells us how fast the universe was expanding when it was much younger.
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Molecular Speeds: What is the total translational kinetic energy of the gas in a classroom filled with nitrogen at 1.01 × 105 Pa at 20.7°C? The dimensions of the classroom are 4.60 m × 5.20 m × 8.80 m. The Boltzmann constant is 1.3806503 × 10-23 J/K, R = 8.31 J/mol ? K, and NA = 6.022 × 1023 molecules/mol.
Fill in the blank(s) with the appropriate word(s).
Charge in an Electric Field: A small object with a 5.0-?C charge is accelerating horizontally on a friction-free surface at 0.0050 m/s2 due only to an electric field. If the object has a mass of 2.0 g, what is the magnitude of the electric field?
A. 2.0 N/C B. 4.0 N/C C. 0.0020 N/C D. 0.0040 N/C E. 1.0 N/C
A magnifying lens with a focal length of 30.0 cm has what maximum magnification? (Assume the near point is 25 cm)
a. 2.2 b. 0.8 c. 31.0 d. 1.8 e. 30.0