Oscillation properties of a second-order impulsive delay differential equation

For the second-order delay differential equation with impulsive conditions y(tκ+)-y(tκ−)=bκy(tκ−), y′(tκ+)-y′(tκ−)=bκy′(tκ−), an explicit necessary and sufficient condition for all bounded solutions to be oscillatory is obtained by the comparison theorem on bounded oscillation of the impulsive differential equation with the corresponding nonimpulsive differential equation.