[单选题]
Wavefronts travel across a boundary between two media as shown.
Which of the following correctly describes the change, if any, in the speed, wavelength and frequency of the waves as they pass from across the boundary?
A. Speed is Increases; Wavelength is Increases;Frequency is Unchanged
B. Speed is Unchanged; Wavelength is Increases;Frequency is Decreases
C. Speed is Increases; Wavelength is Unchanged;Frequency is Increases
D. Speed is Decreases; Wavelength is Decreases;Frequency is Unchanged
参考答案: D
本题详细解析: Explanation:
It can be seen on the diagram that when the waves cross the boundary, the wavelength decreases. At a boundary, the frequency of a wave is unchanged because the number of waves entering the boundary every second must equal the number of waves that leave the boundary every second.
From the relationship $v=fλ$, if f remains constant and $λ$ decreases, the $v$ must also decrease.
