Wave model vs Photon model

[Eden Breslauer-Friedman 2A]

Describe the nature of light as electromagnetic radiation (wave model) and as a stream of photons (photon model)

I understand from lecture the photoelectric effect contradicts the wave model because increasing the intensity did not always increase or allow electrons to be ejected from metal, showing that the number of photons only mattered if the energy of each was enough to eject an electron. Does this finding, since it contradicts the wave model refer to the photon model of light?

I attached the learning objective from Outline 2 for reference, and would appreciate any insight on the accuracy of my conclusions or how else to understand the difference between the wave and photon models.

Thank you!

[John Pham 3L]

You're correct. The photoelectric effect has results that show that light has particle-like properties as it is a stream of photons. If it had wavelike properties, increasing intensity should have resulted in the ejection of electrons.

On the other hand, the experiment where light is shined through a prism and shows diffractions patterns is an example of the wavelike properties. Constructive and destructive interference of waves produces these diffraction patterns and is evidence to the wavelike properties of light.

[Elena Chen 2E]

Yes, the model of the photoelectric effect refers to the photon model. If light acted as a wave in the photoelectric effect, then the energy of the light would increase as the intensity (amplitude) increased, but as we know now, that does not happen. Therefore, there must be an alternative model for light, which is the photon model. Each packet of energy, or photon, interacts with an electron in the metal (one photon per electron), and if the energy of the photon is high enough, an electron is emitted.

[Ryan Laureano 3I]

Your summary is correct in that the photoelectric effect shows light having particle properties. Along with diffraction patterns, these examples highlight the wave-particle duality which states every particle or quantum entity exhibits both wave-like and particle-like properties. The photoelectric effect shows photons as a particle due to the increasing of intensity of light not affecting the ejection of a electron (which you correctly stated). The diffraction pattern shows photons with a wave-like pattern because of how constructive and destructive interference work to make the pattern (if it was a particle in this situation, the pattern would be just where the slits are).