Answer: By counting the number of troughs per second frequency can be calculated.
Step-by-step explanation:
Frequency of the wave is defined as number of cycles occurring in one second. By counting the number of troughs per second we can calculate frequency of the wave
Amplitude of the wave is defined as maximum displace of the particle from its means position is known as Amplitude.
Wavelength of the wave is defined as distance between two successive crests or troughs.