Answer
See explanation
Work Step by Step
Ray tracing models the actual behavior of light in a virtual scene. For each pixel on the screen, it tries to figure out where the light came from, and what color it is (which can change if it passed through or reflected off a colored object in the scene). Ray tracing can correctly model the behavior of mirrors and refracting objects like glass. It's very computationally expensive and consumer machines cannot do it in real time. While traditional rendering pipeline builds up an image the way a painter paints a picture, drawing the objects in the scene from back to front, so the ones in front obscure the ones behind. It can't correctly model the behavior of a mirror because it only draws objects, it doesn't track the light itself.
