PHY CHEM 7.2 Wave-particle duality

Wien’s Displacement Law

gives relationship between λ of thermal radiation and the temperature at which a black body emits radiation

Wien’s Displacement Law Formula

Photoelectric effect

Experimental evidence of the for the existence of photons comes from the measurement of the energies of electrons produced in the _______

1. No electrons are ejected, regardless of the intensity of the radiation, unless its freq. exceeds a threshold value characteristic of the metal

2. The kinetic energy of the ejected electrons increases linearly with the frequency of the incident radiation but it is independent of the intensity of the radiation

3. Even at low light intensities, electrons are ejected immediately if the frequency is above the threshold.

These 3 are the experimental characteristics of the photoelectric effect:

↑ size of atom = easier to eject electron
↑ work function = harder to eject

___ size of atom = easier to eject electron
___work function = harder to eject

conservation of energy requires that the KE of the ejected electron should obey (give formula)

work function

characteristic of the metal is called ___ (ϕ), the energy required to remove an electron from the metal to infinity, the analogue of the ionization energy of an individual atom or molecule

Wave & Particle

2 Characteristics of EMR

Davisson-Germer experiment

The scattering of an electron bream from a nickel crystal shows a variation of intensity of characteristic of a diffraction experiment in which waves interfere constructively an destructively in different directions

Clinton Davisson & Lester Germer

American physicists that performed the experiment that observed the diffraction of electrons by a crystal in 1925

Diffraction

Interference caused by an object in the path of the waves

G.P. Thomson

he worked in Scotland, almost the same time that Davisson-Germer experiment was conducted. Beam of electrons were diffracted when passed through a thin gold foil

any particle, not only photons, travelling with a linear momentum should have in some sense a wavelength given by the ___. (give name + formula)

TRUE

(T/F) Particle with a high linear momentum has a short wavelength

Wave-particle duality

Joint particle and wave character of matter and radiation is called ___