Concept:When light enters a denser medium, its speed changes, but its frequency is set by the source and does not change.
Explanation:Light travels from a less dense medium to a denser medium.
The optical density increases, so the speed of light decreases.
Frequency depends only on the source of light, not on the medium.
Thus, as the medium changes, frequency remains constant.
Using
v=fλ, when speed decreases and frequency is constant, wavelength must also decrease.
Answer:Speed decreases and frequency remains the same.
Correct option: D.