1.21- understanding how light acts as a wave

[Rakhi Ratanjee 1D]

1.21 Q: Pick the observation that best supports the idea that electromagnetic radiation has the properties of particles. Explain reasoning.
A: photoelectric effect because if light were acting as a wave then the intensity would be proportional to amplitude (size) of the wave and bigger waves means greater energy.

I understand that the photoelectric effect depicts light as a particle but I do not understand the wording of the answer. How are intensity, amplitude and wavelength of light related?

[Samantha Joseph 1F]

To my understanding, intensity is unrelated to wavelength/frequency but it is related to amplitude, as the question's answer explains briefly. Greater amplitude means more photons are emitted, which causes an increase in intensity.

[Eli Aminpour 2K]

The photoelectric effect shows that light has properties of particles. In the experiment, they would shoot photons at certain pieces of metal, but if the photon did not reach the threshold energy, than no electron was ejected. They tested that same light (with the same frequency/wavelength), but the second time increased the intensity (amplitude) of the photon. If light only had properties of a wave, than the electron would have been ejected. However, the electron was not ejected even when the intensity was increased because the energy of a photon is based on frequency, not amplitude.