The pupillary distance (PD) measurement is a requirement for people who want to purchase eyeglasses. Here, find out how to measure your PD using a mirror and a ruler. Share on Pinterest Some eyewear ...

Pupillary distance is the space — measured in millimeters (mm) — from the center of one pupil to another. When you need glasses, an optometrist or an optician will measure this distance to make sure ...

The phrase power factor frequently is used in the electrical and power electronics industry. For example, home, office, and industrial electrical equipment often is fitted with power factor-corrected ...