Answer :
The most appropriate phrase to describe the frequency of a wave is 1. 'how often', as frequency is measured in how many cycles of the wave occur per second, typically measured in hertz (Hz).
When describing the frequency of a wave, the phrase that would be most appropriate is 'how often'. The frequency of a wave refers to the number of times the wave completes a cycle, such as a crest to crest or trough to trough, at a given fixed point per unit time. It is usually measured in hertz (Hz), where 1 Hz is equivalent to 1 cycle per second. When you're observing the frequency of wave motion, such as a water wave moving across the surface causing an object like a seagull to bob up and down, you're counting how often those up and down oscillations occur within a specific duration.
Therefore, option 1, 'how often', is the correct answer to describe the frequency of a wave.
