An old bone sample contains 321. grams of carbon and its activity is 947. decays/min. (5730. yr half life of Carbon-14)
(a) How many thousand years old is the sample?
(b) What will be the activity of the sample 2000. yrs from now?
(a) 14. thousand years old
(b) 743. decays/min
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Semiconductor elements are "doped" in order to
A. make them less susceptible to temperature changes. B. make them electrically charged. C. eliminate the possibility of incomplete bonds. D. increase their electrical conductivity.
A friend produces a Geiger counter to check the local background radiation
It ticks. Another friend, who normally fears most that which is understood least, makes an effort to keep away from the region of the Geiger counter and looks to you for advice. What do you say? A) Run away as fast as you can! B) The Geiger counter is emitting radiation. C) The Geiger counter is detecting naturally occurring radiation from your body. D) Wear heavy clothes.
What is the source of the magnetic field in the Crab Nebula? What is at the very center?
A.) A black hole. B.) A neutron star. C.) A white dwarf. D.) Nothing. The star blew itself up. E.) An excited Nebula.
One day while measuring acceleration with his pulse as a timing source, Galileo became so excited that his pulse rate increased. His results for acceleration that day were probably
A. unchanged. B. higher than usual. C. lower than usual. D. more accurate than usual.