failure of classical physics:
blackbody radiation
- classical physics would have predicted that as the wavelength was reduced, the intensity would increase forever
- (assumed energy is continuous)
source of electromagnetic radiation in blackbody radiation is oscillators
- kinetic interactions between matter particles reduce in charge acceleration and dipole oscillation, producing electromagnetic fields
- higher temperature
higher energy emitted - impossible to excite oscillators to next energy level (gap too large, so infinite energy is required, therefore break)
- creates Planck distribution of intensities
- shows that energy is quantised
photoelectric effect
- shining electromagnetic radiation onto surface of metal
- when radiation interacts with surface of metal, electrons were freed from surface of metal
particle model of electromagnetic radiation:
- photons knock electrons off of the surface, but at low energies, the photon does not have enough energy to move the electron
plotting a graph of the intensity of the electrons emitted and the wavelength of light:
often represents frequency in chemistry is the threshold at which electrons remove electrons - provides evidence that energy is discrete due to sharp turn (if continuous, would be smooth)
conservation of energy states that:
where
- 1 photon frees 1 electron