When a Beam of Light That Is Traveling in Air

Multiple Choice

When a beam of light that is traveling in air is reflected by a glass surface,there is

A) a 90° phase change in the reflected beam.
B) no phase change in the reflected beam.
C) a 180° phase change in the reflected beam.
D) a 60° phase change in the reflected beam.
E) a 45° phase change in the reflected beam.