The accuracy of the seminal equation 2 has been verified in a variety of complicated geometries. For low-Q cavities, such as plasmonic nanoresonators that are used for sensing, equation 2 has been shown to predict both the shift and the broadening of the resonance with a high accuracy, whereas equation 1 is inaccurately predicting both. For high-Q photonic cavities, such as photonic crystal cavities or microrings, experiments have evidenced that equation 2 accurately predicts both the shift and the Q change, whereas equation 1 accurately predicts the shift only.