Driving & Driving Test Tips: stoplights, front bumper, stoplight

Question
Can you tell me what constitutes running a red light? Some yellow lights stay yellow for a very short time and as I cross the intersection I can sometimes see the light turn red as the view of it reaches the top of my windshield.
 I have done some research on the internet and some people will say something like "when the car " or "when you" pass this or that line or are "in" the intersection.......blah blah.
  But which part of the car? Tne front bumper? The front wheels? The back bumper? Is there a way to know how long a yellow light will stay yellow? And if I try to suddenly stop for a yellow light and someone hits me from behind can it be my fault? I have been told before that anytime someone hits you from behind it is their fault. Is this true? What if I try to stop for a yellow light and after I stop my front bumper is past the white line and then the light turns red? I have also been told that if a stoplight has cameras there must by law be a sign at the intersection stating such. Is that true? Thank you.

Answer
Running a red light is passing by the limit line (usually a line behind the crosswalk or the crosswalk line furthest from the intersection) by your front tires after the lights have turned to red.  Usually you won't get a ticket if you don't go into the intersection but if you do, most officers will cite you for this vioaltion.