On this Wikipedia the language links are at the top of the page across from the article title. Not to ldr valentine’s day gifts for him confused with Photoresist. LDR 1480405 6 7 HDR Enhancer 1. A photoelectric device can be either intrinsic or extrinsic.

An intrinsic semiconductor has its own charge carriers and is not an efficient semiconductor, for example, silicon. Large CdS Photocell from a street light. A photoresistor is less light-sensitive than a photodiode or a phototransistor. The latter two components are true semiconductor devices, while a photoresistor is a passive component that does not have a PN-junction. Photoresistors also exhibit a certain degree of latency between exposure to light and the subsequent decrease in resistance, usually around 10 milliseconds. The lag time when going from lit to dark environments is even greater, often as long as one second. This property makes them unsuitable for sensing rapidly flashing lights, but is sometimes used to smooth the response of audio signal compression.

The internal components of a photoelectric control for a typical American streetlight. The photoresistor is facing rightwards and controls whether current flows through the heater which opens the main power contacts. At night, the heater cools, closing the power contacts, energizing the street light. Photoresistors can be placed in streetlights to control when the light is on. Ambient light falling on the photoresistor causes the streetlight to turn off. Thus energy is saved by ensuring the light is only on during hours of darkness.