That means that the camera is running when the green light is on. (Facetime, Skype)
I would reset the PRAM.
Power down the computer.
Press the power button
Hold Command, Option, P,R all at the same time.
This will speed up boot times.
Also make sure that you fully QUIT a program to minimize the CPU usage.
Also check for a SOFTWARE UPDATE
Also you could upgrade the ram in the computer.