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xDespite hypothesising that amplitude (intensity) of a wave was related to a wave’s eng which should result in increase max Ekof electrons, did not explain why Max Ekchanged with freq of incident light used. xCould not explain work function/ threshold freq Support for the particle model = Flaws in wave model from photoelectric effect experiment Particle diffraction –Matter scattering Davisson and Germer bombarded nickel crystals with electrons xSpeed of electrons known due to set accelerating voltage xMaximum and minimum intensities were located at different angles recorded by a detector (Similar to young’s double slit) Electrons had undergone interference(once thought to be an exclusive wave property) Electrons fringe spacing and path difference used to calculate wavelength of electron (0.14nm) this value verified De Broglie’swavelength formula: using known velocity controlled by the accelerating v & mass of an electron (9.11 x 10-31kg)Main relationships for the experiment:  EkVoltage  Ek= mv2 W (work on electron) = q (charge: 1.6x10-19C) x V (volts) = EkDouble accelerating voltage: 2 xEk= Increases v by factor of √ = Decreases wavelength by factor of √ Absorption/emission spectra Incandescent lights–electricity sent through gas vapour to excite electrons –Electrons absorb eng releasing thermal eng as photons (Evidence for quantised discrete eng levels) Support for the dual nature of matter____________________ xDiscrete eng levels for particles (electrons) –Electrons moved in wavesinside their eng levels (quantised) xStanding waves are the eng levels electrons exist within; only certain λof light will promote electrons (resonance) Circumference of electron orbit = = nλ (standing wave) forming a stable orbit x(n=1,2,3 ...) n = 1 (ground level), n=2 (1stexcitation state), etc. If an integral number of wavelengths cannot fit into the circumference of electron orbit, destructive interference occurs and the orbit (wavelength) is not an eng level Left to right: n =3,4,5,6Light and Matter Wave Model Particle Model xLight beams cross paths undisturbed xRefraction (Snell’s Law)xInverse Sq. law (I ) xLinear Propagation xReflection xLinear Propagation xReflection xInverse Sq. law (I ) Could not explain: xPhotoelectric Could not explain: xRefraction xWaves–transfer of eng without the net transfer of matter xMechanical waves–Requires a medium to propagate through xWave Amplitude–maximum displacement a particle in a mechanical wave has from its origin xPeriodic Wave–Source of disturbance undergoes continual oscillation producing a constant wave Light Properties –Eng, no mass, no chargen = 0 n = 1 n = 1 n = 1 n = 1 n = 2 n = 2 n = 2 Second minima Location of node Swap terminals of battery (+ve terminal faces cathode) for -ve voltage at cathode (location of light) –This gives the max Ek Monochromatic light used for this experiment-ve terminal towards cathode:Accelerating voltage(voltage not impeding photocurrent) -ve terminal towards cathode: Accelerating voltage(voltage not impeding photocurrent)Stopping voltage–How much work done by load to stop