Radioactive Decay: The atom 40K decays radioactively to the gas 40Ar. An ancient rock is found to contain enough 40Ar gas to indicate that 77.0% of the 40K in the rock has decayed to 40Ar since the rock solidified. (Any previous argon would have boiled out of liquid rock.) How long ago did the rock solidify? The half-life of 40K is 1.25 billion years.
A. 2.65 billion years
B. 0.471 billion years
C. 1.80 billion years
D. 0.324 billion years
Answer: A
You might also like to view...
Which of the following is not a major reason why astronomers would like an observatory on the far side of the Moon?
A) Telescopes on the Moon could see objects in all parts of the sky equally well, whereas telescopes on Earth can see only portions of the sky that depend on their latitude. B) Radio astronomy would be advantageous on the Moon because human radio transmissions are less likely to cause interference, especially on the far side of the Moon. C) It would be possible to put telescopes for ultraviolet and X-ray astronomy on the surface, unlike the case on the surface of the Earth. D) Telescopes on the Moon could observe stars even when it is daytime on the Moon.
The energy transported by a wave is proportional to the square of the frequency of the wave
Indicate whether the statement is true or false
Sketch possible interatomic potentials as a function of interatomic separation for two materials A and B. Material A has a high melting temperature and vaporization temperature and a high elastic modulus. Material B has a low melting and vaporization temperature and a low elastic modulus.
What will be an ideal response?
Energy Levels: In making a transition from state n = 1 to state n = 2, the hydrogen atom must
A. absorb a photon of energy 10.2 eV. B. emit a photon of energy 10.2 eV. C. absorb a photon of energy 13.58 eV. D. emit a photon of energy 13.58 eV.