Why aren't the three readings for background radiation in Procedure 1 identical?
Background radiation comes from cosmic rays and local radioactive sources in a
random way, and a time of 1 minute is too brief to obtain identical readings but these
variations will average out over longer times.
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The spectra of the coolest stars contain strong absorption features (or lines) of
a. TiO molecules. b. ionized helium. c. helium. d. hydrogen. e. All of the other choices are correct.
Light entering a transparent material from the air:
a. bends toward the normal. b. bends away from the normal. c. bends toward its source. d. does not bend. e. is entirely reflected.
Would water molecules in Venus's atmosphere, whose temperature is 740 K, eventually es-cape into outer space? Note that a water molecule has a mass that is 18 times that of a hy-drogen atom. The escape velocity of Venus is 10 km/s. For comparison, a hydrogen atom has an average velocity of 2.5 km/s at a temperature of 300 K.
a. No, the average velocity of water molecules is 0.9 km/s. b. Yes, the average velocity of water molecules is 0.9 km/s. c. Yes, the average velocity of water molecules is 2.1 km/s. d. No, the average velocity of water molecules is 2.1 km/s. e. Yes, the average velocity of water molecules is 19 km/s.
If the Earth rotated on its axis more slowly than it does now:
A) its months would be longer B) its years would be shorter C) its days would be shorter D) its days would be longer E) its months would be shorter