What is the function of a light-dependent resistor (LDR)?

A light-dependent resistor (LDR) is a sensor that changes its resistance based on the intensity of light.

LDRs are made of a semiconductor material that exhibits photoconductivity, meaning its electrical conductivity changes when exposed to light. When light falls on the LDR, the electrons in the semiconductor material absorb energy from the photons and move to higher energy levels, increasing the number of charge carriers and thus reducing the resistance of the LDR. Conversely, when the light intensity decreases, the number of charge carriers decreases, and the resistance of the LDR increases.

LDRs are used in a variety of applications, including automatic street lighting, burglar alarms, and camera light meters. In street lighting, LDRs are used to detect the ambient light level and switch the lights on or off accordingly. In burglar alarms, LDRs are used to detect changes in light levels caused by an intruder entering a room. In camera light meters, LDRs are used to measure the amount of light falling on the camera sensor and adjust the exposure accordingly.

Overall, LDRs are a simple and effective way to sense light levels and can be used in a wide range of applications.