## Homework 1.21

$c=\lambda v$

Matthew Leung 1B
Posts: 20
Joined: Fri Jun 23, 2017 11:39 am

### Homework 1.21

Question: from the following list of observations, select one that best supports the idea that electromagnetic radiation has the properties of particles. Black-body radiation, electron diffraction, atomic spectra, and photoelectric effect.
I understand that photoelectric effect gave rise to the concept of photons and that electron diffraction showed the wave-like properties of light but I am not clear what black-body radiation and atomic spectra don't support the particle model. Can someone please explain this?

Stephanie H
Posts: 20
Joined: Fri Jun 23, 2017 11:39 am

### Re: Homework 1.21

The black-body radiation lead Planck to propose his hypothesis that matter and radiation exchange energy in quanta (packets of energy), essentially Planck proposed the idea of particles properties in light. Planck conducted more experiments, which led to the photoelectric effect, to prove his hypothesis. The photoelectric effect solidified his hypothesis, for the existence of particles in light.

The atomic spectra is just classifying wavelengths with the light color they emit. This led to the idea of spectral lines (radiation of wavelengths) and spectral lines led to the idea of energy levels (electrons in an atom have specific values or energy levels).