# Light dependent resistors

Objective

Learn about LDR. Measure intensity of light and its variation with distance from the source.

Procedure

- Measure the LDR’s resistance, for different light intensities.

- Iluminate LDR using a fluorescent lamp, A1 should show ripples

- Put A1 in AC mode and measure ripple frequency

Discussion

The resistance vary from 1kΩ to around 100 kΩ depending on the intensity of light falling on it. The voltage is proportional to the resistance. The resistance decreases with intensity of light. If you use a point source of light, the resistance should increase as the square of the distance between the LDR and the light source.