Answer the following question given this paragraph: 

A photon isn’t a fixed amount of energy. Instead, the amount of energy in a photon depends on the frequency of the electromagnetic wave. The frequency of a wave is the number of waves that pass a fixed point in a given amount of time, such as the number of waves per second. In waves with higher frequencies, photons have more energy.


Q: The number of waves that pass a fixed point in a given amount of time is called what?

 Choices:

- wavelength of a wave

- spectroscopy of a wave

- spread of a wave

- frequency of a wave

A:
frequency of a wave
