Particle Model Of Light Flashcards
Quantum
Is a discrete (individual or separate) amount
Photon
Is a quantum (particle) of light energy
Black body
Is an object that perfectly absorbs all energy that contacts it when it is cool and emits (radiates) all wavelengths of light when hot
Threshold frequency
Each metal has its own certain frequency where electrons are emitted at or above this frequency
Intensity
When the intensity of light is increased the current of electrons will increase= increased photo current
At threshold frequency
The energy of the photon is equal to the work function so the kinetic energy of the emitted electron is zero
Smallest work function
Requires the least amount of energy to eject an electron, leaving more for kinetic energy
Photocurrent
The flow of electron charge in a photoelectric cell
Photoelectron
An electron ejected out of a metal By an incoming photon that has enough energy to knock it out of its position
Photoelectric supports particle nature of light
A wave could release electrons by heating metal, but not instantaneously. A collision between particles could be an instantaneous release if the energy of the particle is greater than the work required to release the electron
Compton effect vs photoelectric effect
The photoelectric effect ejects one electron per incoming photon, the Compton effect ejects one electron plus a lower energy X-ray
Joule in base units
J= kgm2/s2
Plancks constant in base units
h=kgm2/s
Photons have a mass equivalent to:
E=mc2
Energy of black body
Depends on its temperature not the material it’s made from
Black body curve- temperature increases
As the temperature increases the maximum brightness (peak wavelength) increases and more radiation is emitted at higher frequencies
Wave theory
Predicted that the intensity of the radiation would increase as the black body absorbed more energy and the frequency increased
At high frequencies (short wavelengths) the intensity would be infinite, oscillators vibrate at any frequency and can absorb energy at high frequencies
Classical theory
Said energy is continuous, a continuous stream of waves and more waves emitted would mean larger amplitude
Ultraviolet catastrophe
Is the failure in the classical physics theory at the short wavelengths. Prediction that a hot object would emit its energy most effectively at short wavelengths- this was FALSE
Quantum theory
Energy is not continuous but could only be absorbed or emitted as discrete bundles of quantized energy
Max Planck
Developed new idea to explain blackbody radiation, as the classical prediction and experimental observation by Planck contradicted
Plancks explanation
Walls of the black body contain a bunch of little oscillators which absorb and emit radiation, each oscillator can only have an energy which is an integer multiple of a quanta.
Oscillators at the low energy is more likely than the High energy
Photon model of light
Einstein said all EMR travels as photons=quantized, energy is related to frequency, intensity is related to brightness
Millikan
Discovered there was a linear relationship between Ek and f.
Slope = h
Yintercept = W
X intercept= threshold frequency
