Final answer:
The photon that exits a window pane is the same photon that entered; although its velocity changes while within the glass, its fundamental identity does not.
Step-by-step explanation:
Compared to the photon that enters a pane of window glass, the photon that emerges is A) the same photon. This concept is part of understanding how light interacts with different materials. When a photon enters glass, it is temporarily absorbed and re-emitted by the atoms within the glass.
This process does not change the photon into a different one; it remains the same photon, although its velocity is reduced while it travels through the glass. Upon exiting, the photon resumes its original velocity in air. This phenomenon is part of classical and quantum physics, illustrating the wave-particle duality of light, where photons act as both waves and particles.