What two things must occur in order for a light ray to refract when it strikes
the boundary of a different medium?
A. It must strike the boundary at an angle, and its speed must
change.
B. It must strike the boundary at 45°, and its wavelength must
change.
C. It must strike the boundary at an angle, and its frequency must
change.
D. It must strike the boundary at 45°, and its frequency must change.