Step 5Detecting the light

Amplification circuit

To detect the light that passes through the sample, we're going to use an LDR, or Light-Dependent Resistor.
Though it would be possible to obtain readings by connecting an ohm-meter straight to the LDR, it probably is a better idea to construct a basic amplifier allowing us to use a voltmeter since this will provide bigger differences between slight changes in detected light intensity.

Assemble the amplifier according to the circuit. I used a TL081 opamp. Then measure the voltage between 0V and Output; this will vary depending on the light falling onto the LDR.


Putting the "L"in LDR

Place a cuvette or test tube just behind the slit. Now, glue the LDR in place so that the light passing through the cuvette will hit the LDR.