Nearly all galaxies contain Cepheid variable stars. Why, then, do we determine the most distant galaxy distances using white dwarf supernovae rather than Cepheids as standard candles?
A) White dwarf supernovae are much more reliable standard candles than Cepheids.
B) White dwarf supernovae can be observed in galaxies that are too far away for us to see individual Cepheids.
C) White dwarf supernovae are more common than Cepheids.
D) White dwarf supernovae can be detected with a single observation, while it takes many observations to measure a Cepheid's light curve.
B) White dwarf supernovae can be observed in galaxies that are too far away for us to see individual Cepheids.
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The seasonal changes on Mars create:
A) remarkable changes in size of the two dry ice polar caps. B) changes in the dark features noted from Earth by telescopes long ago. C) huge dust storms that can enshroud the planet's disk. D) great changes in the barometric pressure as the atmosphere freezes and sublimes. E) All of these are correct.
What is the wavelength of a monochromatic light beam, where the photon energy is 4.14 × 10^?19 J? (h = 6.63 × 10^?34 J?s, c = 3.00 × 10^8 m/s, and 1 nm = 10?9 m)
a. 160 nm b. 480 nm c. 72 nm d. 187 nm e. 915 nm
Which of the following is a strong acid?
a. Citric acid b. Nitric acid c. Phosphoric acid d. Acetic acid
If the headlights on a car are separated by 1.3 m, how far down the road can they be resolved if the angular resolution of the eye is 5.0 × 10-4 rad and the person has excellent vision?
A) 1.3 km B) 5.0 km C) 4.8 km D) 0.65 km E) 2.6 km