The half-life of carbon-14 is 5730 years. explain how to figure out the age of a substance that has 25% carbon-14 remaining. a) multiply 25% times 5730 years since only 25% of the carbon remains. b) divide 5730 years by 2 since carbon has gone through two half-lives. c) multiply 5730 years by 2 since two half-lives have gone by for carbon. d) multiply 4 times 5730 years since carbon has gone through 4 half-lives.

Materials will have different energies associated with the electrons inside them. this is related to how strongly bound they are by their work function. if we sandwich a material with a very low energy between two materials with a high energy, we create a trap for an electron. if this trap is very narrow in one direction in comparison to the others, this is approximately a 1-dimensional box that confines the electron. what is the lowest energy of an electron in the box if the thinnest direction across the materials is 4.81 nm?