** Phase Shift vs Phase Angle
**

Phase shift and phase angle are two key aspects of a wave. This article presents the definitions, similarities and finally the differences between phase shift and phase angle.

**What is Phase Angle?**

To understand phase angle, one must first understand the basic behaviors of a wave. A travelling wave can be defined using the equation Y(x) = A sin (ωt – kx); where Y(x) is the displacement on the y axis at point x, A is the amplitude of the wave, ω is the angular frequency of the wave, t is the time, k is the wave vector or sometimes referred as wave number, x is the value on the x axis. The phase of a wave can be interpreted in several ways. The most common is (ωt – kx) part of the wave. It can be seen that at t=0 and x=0, the phase is also 0. ωt is the number of total revolutions the source of the wave has done when the time is t, (ωt – kx) is the total angle the source has turned. The above described wave equation is valid only for sinusoidal waves having a zero displacement and zero velocity at time equals zero. A more advanced form of the wave equation can be written as Y(x) = A sin (ωt – kx + φ) where φ is the initial phase of the wave. This is a complete wave equation. The ωt+φ can be considered as the phase angle of the wave. The phase angle of the wave describes how many turns the source wave has made. The kx part of the wave equation describes the length the wave has travelled. The whole (ωt – kx + φ) part of the wave equation describes the position of the wave from the origin as well as the displacement from the equilibrium point.

**What is Phase Shift?**

Phase shift is a change in the phase angle. This can happen due to various external reasons. First, a clear understanding of hard reflection is needed to understand the most common factor of phase shift. When a wave (assume light) travelling in a medium with a refractive index of n_{1} is reflected from a medium having a higher refractive index than n_{1}, the angle of the wave shifts by 180 degrees. This is the phase shift involved in reflection. It is important to note that refractions do not create a phase shift. When a wave travels on a medium, the phase of the wave is dependent on the medium itself. The real length a wave travelled multiplied by the refractive index of the medium is known as the optical path length of the light ray.

• Phase angle is a property of the wave and dependent on reflections, the medium, and other external factors. • Phase shift is the changes in the phase of the wave due to external factors. • Both of these quantities are measured in radians or degrees. |

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