Question

What is Light Dependent Resistor? How it is used for measurement of Intensity of light?

Answer 1

A light dependent resistor (LDR) is a component that has a resistance that changes with the light intensity that incident upon it. LDR have a resistance that decreases with an increase in the intensity of light falling upon the apparatus.

LDR is used to measure the intensity and the colour of visible light. It is because, the spectral sensitivity of LDR’s peaks are somewhere in the green region where the human eye is most sensitive. The intensity is varied nonlinearly as follows:-
$\frac{I}{I_0}={\left(\frac{R}{R_0}\right)}^{\gamma }$
Where R₀ is the resistance at the intensity I₀, $\gamma$is LDR’s constant and is usually given in the data sheet of the device. Generally, LDR’s constant is around 0.6 to 0.8.