What is a lumen used to measure?

A lumen is a unit of measurement that quantifies the amount of light that is emitted by a light source in a particular direction. It is part of the International System of Units (SI) and specifically pertains to luminous flux, which describes the perceived power of light as it is visible to the human eye.

When evaluating the options, it’s clear that a lumen directly relates to the measurement of light, making this choice the most appropriate. The other options refer to completely different physical phenomena; for instance, electricity is typically measured in units like volts or amps, temperature is measured in degrees Celsius or Fahrenheit, and pressure is measured in pascals or psi. Thus, the definition and context of a lumen distinctly align with the measurement of light.