chapter 13 - quantum Flashcards

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1
Q

photon energy

A

E = hf
or = hc/λ

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2
Q

Plancks constant (h)

A

6.63 *10^-34

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3
Q

photons

A

quanta of energy of electromagnetic radiation

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4
Q

how does the photon energy equation show wave and particle properties of photons

A

E = hc/λ
has wave elements due to the λ
has particular elements due to the E

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5
Q

eV

A

electron volt
energy gained/ lost when an electron moves across 1v
1eV = 1.6*10^-19 J

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6
Q

LED

A

an electron is transfered across a pd
gains energy (eV)
electron emits energy as a photon
eV = hf
plot eV against f
grad = h

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7
Q

power of a laser

A

E = hf for one proton so
P = nhf
if n = no protons per sec

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8
Q

photoelectric effect UV vs visible light

A

when high freq light is shined onto a charged plate it releases photoelectrons
when low freq eg visible light no effect

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9
Q

gold leaf electroscope

A

the plate has a charge which it passes down the stem and gold leaf - so the like charges repel
when UV light is shined onto this it becomes discharged so can demonstrate the photoelectrc effect as the leaf is discharged

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10
Q

hwo is the photoelectric effect evidence for wave partical duality

A

if just a wave would discharge after a lomg enough / high enough intensity so must have particles (photons)

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11
Q

conclusions from the photo electric effect that arent explained by wave theory

A
  • photo electrons only emitted above threshold freq
  • no. electrons is prop to intensity
  • electrons emitted have a variety of KE up to max KE
  • max KE ^ with f
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12
Q

photon model - photoelectric effect

A

EM waves are released as discrete packets (photons)
a photon transfers all energy to one electron
the elctron will leave the surface if it has enough energy to leave
if not enough the metal just heats

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13
Q

work function energy

A

minimum amount of energy needed for one electron to be released
(depends on the metal)
⍉ = hf₀
if f>= f₀ electron is released
if f < f₀ just heats up

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14
Q

electron KE eq

A

KE = hf - ⍉ = h(f - f₀)
E = KE + ⍉

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15
Q

finding max KE of emitted electrons

A

Vs = stopping voltage - voltag eat which electrons are attrcated back to previous plate - dont reach other side
eVs = max KE (I = 0)
graoh of KE againts f
KE = hf - hf₀

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16
Q

de broglie λ

A

E = hc/λ = mc^2
λ = h/mv = h/p
shows the λ of an electron

17
Q

double slit experiment

A

matter fired through a double slit should give the same pattern as the slits (||) but whenelectrons are fired through a double slit an interference pattern is produced (|||||)
but when the slit is observed they give the exceoted || pattern
shows wave particle duality

18
Q

electron gun

A
  • filament is heated
  • electrons gain KE
  • some escape through thermonic emission
  • high pd accelerates towards anode
  • gains high KE
  • pass through hole in anode (makes electron beam)
19
Q

linear accelerator

A
  • series of electrodes
  • accelerates electrons several times
    λ = h/ root(2meV)
    λ ∝1/ root(v)
20
Q

electron diffraction

A

in an evacuated tube - an electron gun is fired towards a graphite target and onto a phosphor screen
creates rings of maxima

21
Q

diffraction rings

A

the grating is graphite so diffraction is in all directions and makes a ring
nλ = d sinθ
if v increases rings get smaller/ closer
d = h/mvsinθ = spacing between atoms

22
Q

wave particle duality

A

λ = h/mv
electrons act like a wave - have wavlength, create interference patterns (go through difraction)
act like a particel - have mass and charge - are accelertated by electric field, deflected by magnetic field

23
Q

PHOTO ELECTRIC EFFECT

A
  • photon has energy (E = hf)
  • one to one relationship with electrons
  • if energy of the photon is > work function of the metal an electron is released
  • energy transferred from photon (hf ) = work function + KE max
  • if energy is less the metal heats it - no electron is released
  • intensity changes no. photons and no. photoelectrons (if f> threshold freq) but doesn’t effect KE max