Reversing a Photoresistor
Suppose that you have a divider like the one below and the DC source is the AC signal (using DC helps with the simulator)







simulate this circuit &ndash; Schematic created using CircuitLab

If the photo-resistor is in place of R1 then the output behaves like shown below and the output voltage increases as the resistance lowers (more light)


if the photo-resistor is in place of R2 then the output behaves like shown below and the output decreases when the resistance lowers (more light)



In both graphs the vertical axis is the output voltage and the horizontal axis is the resistance value (starting from left side and increasing to the right)