I need to use an operational amplifier as a comparator to indicate if the volume of mauby in a clear glass bottle is below a certain level. I must use a double potential divider arrangement (a bridge) with a LDR as the input transducer and a LED as the output transducer. The potential dividers must be connected across the positive of one power supply. LED in forward bias. LDR of resistance 3MΩ in dark and 3kΩ in light,LED with protective resistor in series with it,3 fixed equal resistors chosen from a set of resistors ranging from 100Ω to 5MΩ,741N op amp chip, 2 15v stabilised power supplies, glass bottle 3/4 filled with mauby, identical glass bottle 1/2 filled with mauby, small laser. What to do??....???

 

is it an assignment?
do you want to know how to connect the parts?

 

yeah..n probably explain how it'll work

 

try these for help
http://www.technologystudent.com/elec1/opamp3.htm
remove the buzzer connect emittter to GND and add LED to collector of transistor