This circuit uses the LM324 to give an improvement on the basic OP-AMP circuit. This time four voltages are being compared, however they are not being compared against each other, but all are being compared seperately with the first potential devider. If any of the LDRs resistance falls to a point where the voltage on it's potential devider exceeds that of the first potential devider, its corresponing LED will light.
So lets say for example the voltage emmited from the first potential devider (The two resistors on the left) is 2V. The Voltage of potential devider 2=3V, potential devider 3=1.5V, potential devider 4=2.5V and potential devider 5= 0.5V. The result- LEDs 1 and 3 will light, as these voltages exceed 2V. The other two LEDs will remain unlit as the Voltages are below 2V.