What properties of waves causes the photoelectric effect

[Photolicktrick]

What properties of waves caused the photoelectric effect to indicate the fact that light was quantized. Why couldn't it be explained by light waves being emitted at the same frequency. I am a little confused about why light couldn't still be a wave. Couldn't the photoelectric effect be explained because many light waves of the same frequency and thus the same energy be responsible for the fact that electrons only get exited by light of a certain energy. I just don't understand what quantization has to do with it.

 

[Hercuflea]

The photoelectric effect is the dominant mechanism for low energy light wavelengths impacting high atomic number elements. It hints at electron energies being quantized, because only certain wavelengths of light are absorbed by the material and their energy is converted into the electrons' kinetic energy. If electron energies were a spectrum rather than being quantized, there would be a continuous spectrum of wavelengths of light being absorbed rather than a finite number of wavelengths.