Author Question: Suppose you find a rock that contains 10 micrograms of radioactive potassium-40, which has a ... (Read 69 times)

tsand2 · **on:** Jul 27, 2018

Suppose you find a rock that contains 10 micrograms of radioactive potassium-40, which has a half-life of 1.25 billion years.

By measuring the amount of its decay product (argon-40 ) present in the rock, you conclude that there must have been 80 micrograms of potassium-40 when the rock solidified. How old is the rock?
A) 3.75 billion years B) 2.5 billion years C) 5.0 billion years D) 1.25 billion years

Question 2

What is Cygnus X-1?

A) the leading candidate for an observable black hole binary system
B) a millisecond pulsar with three Earth-like planets around it
C) the brightest star in the constellation Cygnus
D) the first gamma-ray burster to be spotted in other wavelengths as well
E) the strongest X-ray eclipsing binary system in the sky