Answer:
The distance between successive crests decreases
Step-by-step explanation:
First some definitions :
Period: The time it takes to make a complete wave or vibration is measured in seconds (s) and is represented by an uppercase T. It is also the time it takes for a particle to perform a complete oscillation.
Frequency: It is the number of cycles produced per second. The frequency is indicated by the lowercase letter f. It is measured in cycles / second or Hertz (Hz). It coincides with the number of oscillations per second that a point makes when it is reached by the waves and shares an inverse relationship with the period (T).
The only way to increase the frequency of a wave at constant speed is to generate an increase in its period.
This means decreasing the distance between successive waves.