I read some post related to this and what I got is LED can generate small photo current when you throw light towards it.
I also tried with LM358(Op-Amp),I connected in reverse bias and got same result.
But my question is when I connected LED Anode to BC547 Base and cathode to GND(as shown in attached file),
I mean in forward bias it worked!and it was able to switch LED on (not fully but ther is "some" light) which is connected to collector?
i mean to use LED as sensor it should work in reverse bias?they why it worked with BC547 in forward bias?please tell me I am very curious to know about this..