# Phase angle

In the context of phasors, phase angle refers to the angular component of the complex number representation of the function. The notation ${\displaystyle A\angle \!\ \theta ,}$  for a vector with magnitude (or amplitude) A and phase angle θ, is called angle notation.

This notation is frequently used to represent an electrical impedance. In this case, the phase angle is the phase difference between the voltage applied to the impedance and the current driven through it.

In the context of periodic phenomena, such as a wave, phase angle is synonymous with phase.

## Bioelectric impedance

In bioelectrical impedance analysis in humans, an estimate of the phase angle can be obtained and is based on changes in resistance and reactance as alternating current passes through tissues, which causes a phase shift. The measured phase angle therefore depends on several biological factors. Phase angle is greater in men than women, and decreases with increasing age.[1]

## Astronomy

In astronomy, the phase angle is the angle between incoming illuminating rays (generally from the Sun) and rays reflected off the object, generally as seen by an observer.

## References

1. ^ Barbosa-Silva, MC; et al. (2005). "Bioelectrical impedance analysis: population reference values for phase angle by age and sex". American Journal of Clinical Nutrition. 82 (1): 49–52. doi:10.1093/ajcn.82.1.49. PMID 16002799. Retrieved 3 April 2016.