Now consider ω ω = ω ω 0 , i.e. the B 1 field oscillates at the same rate the dipole exposed to the B 0 field does. That is a case of resonance. Then at specific points in time, namely t = ( 2 n + 1 ) π π ω ω 1 2 + Δ Δ ω ω 2 , the dipole will flip, going to the other energy eigenstate [ 0 1 ] with a 100% probability. When ω ω ≠ ω ω 0 , the probability of change of energy state is small. Therefore, the resonance condition can be used, for instance, to measure the magnetic moment of a dipole or the magnetic field at a point in space.