Want To Learn Electronics..plz Help!!

Hey,I am pretty new to electronics.
I plan to make a line follower with obstacle avoidance for which I would need an infrared emitter detector..
This is what I already know..The ir emits rays that strike an obsatcle and the reflected rays fall upon the detector which is a photodiode.considering the fact that a photodiode works on reverse bias where breakdown occurs and the reverse current is generated.(electric signal)
Now what I want to know is what happens to this reflected ray..???What does a photodiode do to it???
Does it have any specific voltage like (say 1.7volts or something)??
PLZ REPLY!!!

I think you need to start on simpler things

The working portion of most diodes are encased in an plastic that protects it from light because light hitting a PN junction causes a current to flow and you don't want that noise in most circuits. A photo diode is encased in a plastic that allows light to pass into the PN junction, where it generates a current when the light reflected from the obstacle hits it.

That's the general idea, you can get more details in many books by looking up photodiode or phototransistor, or by searching online. For example wikipeda has a discussion on photodiodes.

i think you should start easier