A ray diagram showing refraction at the boundary between air ... and bends away from the normal by the same angle. So if a wave slows down, its wavelength will decrease. The effect of this can ...

When a wave or light ray moves from one medium to another its speed changes. The direction of the ray may also change. This property of waves is called refraction and commonly occurs with light rays.

The P wave amplitude in lead II > 2.5 mm, or The upward deflection of the P wave in lead V1 > 1.5 mm in amplitude.