Real-Life Math
Nuclear physicists try to explain the big picture by looking at its smallest pieces. These highly trained individuals strive to understand our universe by looking at subatomic particles.
They "look" at these particles through the window of mathematics. Nuclear physicists use math in everything they do.
Byron Jennings is a theoretical nuclear physicist, and he's working on a project called the solar neutrino problem. According to calculations, the nuclear reactions on the sun should emit a certain number of subatomic particles called neutrinos.
But when the physicists look for these particles, there aren't as many as there should be. "I'm trying to explain why [by] using math," Jennings says.
He also uses math on another of his projects. This time, math is used to measure the amount of energy it takes to excite the nucleus of an atom. (In the scientific context, "excite" means to put the particles into a state of higher energy.)
If you know the precise amount of energy a nucleus must absorb to get excited, then you can figure out whether that atom is present in a substance.
Recently, nuclear physicists have developed a machine that uses gamma rays (high-energy rays) to detect bombs. It's called a contraband detection system (CDS).
Most plastic explosives are high in nitrogen content. The contraband detection system was developed on the basis that nitrogen can be detected using a phenomenon called gamma resonance absorption (GRA).
Essentially, GRA works because the atomic nuclei of nitrogen absorb gamma rays of specific wavelengths (energy). By scanning the cargo containers or suitcases with the correct wavelength of gamma rays, the CDS can measure the nitrogen density and total density. This information is used by the computer to detect and display significant qualities of the targeted substances -- in this case, bombs.
You've begun work on the CDS. You know that the energy absorbed is measured in electron volts (eV). Normal nitrogen has a mass (energy) of 13134.3997 MeV (million electron volts). Excited nitrogen has a mass of 13143.5720 MeV.
What energy must the gamma ray have in order to be absorbed? State this in units of eV.
Remember: An energy wave (gamma ray) of precisely the correct energy will be absorbed by nitrogen, but not by other elements.