This instructable will explain how to create your own light sensing LED,making some changes,programming the microcontroller,makingit on a breadboard and soldering the circuit.
A short video of it in action:
Step 1: How Can The LED Sense Light?
The LEDs will be sensitive to the light which has the wavelength equal to it or lesser than it.
When light falls on the LED a small voltage is produced this voltage produced can be fed to a microcontroller which can read it and follow the further instructions.