Which instrument is commonly used to measure light intensity?

The instrument that is commonly used to measure light intensity is the lux meter. A lux meter is specifically designed to quantify illuminance, the amount of light that falls on a surface, measured in lux. This makes it particularly valuable in environments where lighting needs to be monitored, such as in workplaces, photography, and environmental studies.

The functioning of a lux meter involves detecting light intensity and providing a direct reading, which makes it the appropriate choice for measuring illumination levels rather than merely electrical characteristics like voltage or current that other instruments can measure. A voltmeter measures voltage, an ammeter measures current, and a multimeter can measure various electrical parameters like voltage, current, and resistance but does not specialize in light intensity.