## Quick Reference

The difference in phase between two sinusoidally varying quantities. The displacement *x*_{1} of one quantity at time *t* is given by *x*_{1} = *a*sinω*t*, where ω is the angular frequency and *a* is the amplitude. The displacement *x*_{2} of a similar wave that reaches the end of its period *T*, a fraction β of the period before the first is said to **lead** the first quantity by a time β*T*; if it reaches the end of its period, a fraction β of the period after the first quantity it **lags** by a time β*T*. The value of *x*_{2} is then given by *x*_{2} = *a*sin(ω*t* + φ). φ is called the phase angle and it is equal to 2πβ.

**From:**
phase angle
in
A Dictionary of Physics »

*Subjects:*
Physics.