Mr Cardwell Physics Flashcards
What does Coherent mean?
Waves of the same type and same frequency maintain a constant phase difference
What does Interference mean?
When Coherent waves meet and Constructive or destructive interference occurs forming a pattern of equally spaced white and dark fringes
What is a Photon?
A Photon is a discrete packet of electromagnetic energy
What is the Photoelectric effect?
The emission of electrons from the surface of the metal by absorbing photons
What is the Work Function?
The minimum amount of energy required for an electron to escape from the surface of a metal
What is eV(Electron-volt)?
A unit of energy and equivalent to the energy gained or lost by an electron moved through a p.d(Potential difference) of 1 volt
What does LASER stand for?
Light Amplification by Stimulated Emission of Radiation
What is Population Inversion?
When there is more electrons in a higher energy state(Excitation) than a low energy state(Ground State)
What is Monochromatic?
Light with only one colour / wavelength
What is Wave-Particle Duality?
It is that all matter exhibits both wave and particle properties but can only be viewed in one way or the other, not simultaneously
What is Electron Diffraction?
When a beam of electrons is passed through a graphite crystal, a diffraction pattern of light and dark concentric rings is observed
What is Youngs Double Slit Experiment?
When two waves that are coherent are shot onto the same screen a pattern of bright and dark fringes is shown. This is the major evidence of light being a wave
What does the Bright and Dark fringes represent?
Bright fringes represent constructive interference(Inphase) and Dark fringes represent destructive interference(Out of Phase)
What is the equation for Youngs Double Slit Experiment?
Fringe Width = Wavelength x Dist from Source to Screen / Dist between the centre of the slits
What if the Double Slit was replaced by lots of slits(A diffraction grating)?
The interference pattern changes to containing fewer but sharper fringes
What is the equation for a diffraction grating?
Dist between 2 slits x sin(Diffraction Angle) = order of diffraction x wavelength
What is Polarisation?
The condition for a wave to be plane-polarised is for the oscillations to be in just one plane (Only in transverse waves)
What is the equation(s) of the Photoelectric effect?
Energy = Planck’s Constant(6.63x10^-34) x Frequency and Speed of light = Frequency x wavelength
What is Threshold Frequency?
The minimum frequency of light which will cause photoelectric emission from the surface of a metal
What is an extra equation of the Photoelectric effect?
Energy of photon = min energy required for an electron to escape + max KE of electron
Describe the Photoelectric graph
It is drawn as a line that has a gradient of planck’s constant and passes through the x axis(Frequency). Where the line intercepts the x axis is the threshold freq
What is
a) The speed of light?
b) Mass of an electron?
c) Electron Charge?
a) 3.00x10^8
b) 9.11x10^-31
c) 1.60x10^-19
What is Emission?
When energy is used to emit a photon which causes the electron to decrease in energy level
What is Absorption?
When an electron absorbs a photon causing the electron to jump to a higher energy state
