An Airy function is a solution to the differential equation y'' - xy = 0. There are two independent Airy functions since the equation is second-order. One solution goes to infinity and the other goes to 0 as x goes to infinity. The Airy function shows up in fields such as quantum mechanics, electromagnetics, and solid state physics. For example, the Airy function is a solution to the Schrodinger equation for a particle in a linear potential. The Airy function is also the solution to the location of interference fringes in the Fabry-Perot interferometer. Only the second Airy function accurately describes physical phenomena, since real physical quantities cannot blow up to infinity.