Quantum Physics Flashcards
Photoelectric Effect
The photoelectric effect is a process in which electrons are emitted from a metal surface when electromagnetic radiation of sufficiently high frequency is incident on the surface
Photoelectron
A photoelectron is an electron emitted from the surface of a material due to the incident electromagnetic radiation
Stopping Potential
The negative potential of collector with respect to emitter which prevents the most energetic photoelectrons from reaching the collector and hence resulting in zero photocurrent
Photon
A photon is a quantum of electromagnetic energy
Work Function Energy
The work function energy of a metal is defined as the minimum amount of energy necessary for an electron to escape from the surface of a material
Threshold frequency
Threshold frequency is the minimum frequency of electromagnetic radiation below which no emission of photoelectrons occurs
Emission Line Spectrum
When a gas is placed in a discharge tube at low pressure with a high voltage applied between the ends of the tube, the gas starts to glow and light is emitted from the electric discharge tube
If this light is examined through a diffraction grating with a spectrometer, a spectrum consisting of well defined, distinct lines is observed
This type of spectrum is known as an emission line spectrum
Absorption Line Spectrum
When white light passes through a cool gas, the atoms of the cool gas absorb photons of certain frequencies to jump from a lower energy level to a higher one
The frequencies of the photons absorbed must have energy equal to the energy difference between two energy levels
After the absorption, the excited atom will eventually return to the lower energy state by emitting the same photons
However, these emissions occur in all directions and therefore have lower intensities
Hence, when the light emerging from the discharge tube is passed through a diffraction grating, light of these frequencies appear to be missing from the continuous spectrum
This continuous bright spectrum crossed by dark lines is called the absorption line spectrum
Continuous Spectrum of X-ray Spectra
The continuous spectrum is due to electromagnetic radiation emitted by the high speed electrons when they are slowed down in the metal target due to interaction with the nuclei of the target atoms
When the electrons decelerate, the loss in kinetic energy emerges as the energy of the X- ray photons
Characteristic X- rays
The sharp spectrum, high energy EM radiation produced when electrons from a higher shell de-excite to a vacancy in the lower shell, created by highly energetic electrons
Heisenberg Uncertainty Principle
If a measurement of the position of a particle is made with uncertainty and a simultaneous measurement of its x-component of momentum is made with uncertainty, the product of the two uncertainties can never be smaller than h/2
