A wave pulse moves along a stretched string where the wave speed is 6m⋅s−1. Upon reaching a junction, it enters a section of the same string in which the wave speed is 12m⋅s−1. Which choice best describes the reflected pulse at the junction?
a) The reflected pulse is inverted because the pulse encounters a faster medium.
b) No reflection occurs; the entire pulse is transmitted.
c) The reflected pulse is upright because the pulse encounters a faster medium.
d) The reflected pulse is inverted because the pulse encounters a slower medium.