quantum physics

HideShow resource information
wave properties light shows?
1. reflection 2. refraction 3. diffraction 4.polarisation
1 of 31
POLARIZATION
Polarized light waves are light waves in which the vibrations occur in a single plane. e.g.
2 of 31
photoelectric effect
when light fell on a metal plate it released electrons instantly. increasing intensity - increased number of electrons released. decreasing the frequency - no electrons emmitted. increase intensity and give more time - no electrons emitted.
3 of 31
if light were a wave ...
increasing the intensity - increase the energy of light. the energy from the light would be evenly spread across the metal and each electron would be given a small amount of energy. eventually the electron would gain enough energy to be released.
4 of 31
THRESHOLD FREQUENCY
minimum frequency of incident light which can cause photo electric emission i.e. this frequency is just able to eject electrons with out giving them additional energy. - f=o/h
5 of 31
WORK FUNCTION
minimum energy required to emit an electron from the surface of a metal
6 of 31
photosynthesis - conclusions
1.electrons were being knocked off the surface 2.reactive metals have outer electrons that can be easily removed 3.intesity is not effected IF is does not react threshold frequency 4. higher frequency = shorter wavelength
7 of 31
behaviour of light?
light travels as a photon which transfer discrete packets of light
8 of 31
explain the photon model of electromagnetic radiation
1. light and other electromagnetic radiation are emitted in bursts of energy - it is quantised 2.photons travel in straight lines 3.when photo released energy changes are discrete amount of quanta 4.energy lost by atom = energy of photon
9 of 31
combine energy equation and wave equation
E=hf and c=fY .... E=hc/Y
10 of 31
ELECTRON VOLT
energy used when the charge of an electron moves through a p.d. of 1V - 1.6X10^-19J = 1eV
11 of 31
explaining the photoelectric effect
a photo collides with an electron in the metal - tranferring energy to give the electron enough energy to be removed. some of the energy is needed to break the bonds holding the electron and the rest used as KE for it to move away. hf=o+KEmax
12 of 31
graph
y=mx+c - KE=hf-o
13 of 31
transitioning
hf = E1-E2
14 of 31
EXCITATION
when an electron gains the exact amount of energy to move up one or more levels
15 of 31
DE-EXCITATION
when an electron gives out the exact amount of energy to move down to its original position
16 of 31
IONISATION
when an electron gains enough energy to be completely removed from the atom. the levels leading up to ionisation have negative vales because they are being compared to the ionisation level - remember electrons must GAIN nergy to move up
17 of 31
line spectra
each transition releases a photo with a set Y and f. we can analyse light by using a diffraction gratting to seperate the light into its different colours - called its line spectra. each element has its own line spectra
18 of 31
inside a fluorescent lamp
1.it is a sealed glass tube 2.contains a small bit of mercury and a noble gas - kept at a very low pressure 3.phosphor powder coated on the inside 4.2 electrodes 1 at each end - wired to an electrical circuit 5.connected to an alternating current(AC)
19 of 31
what happens when the lamp is on?
1.current flows through to the electrodes - creating a p.d. causing electrons to migrate through the gas 2.some collide with gaseous mercury atoms which excite electrons - when moving down levels photons are released
20 of 31
...
3.electrons are arranged in mercury atoms s they release photons in the UV wavelength range 4.when a photon hits a phosphorus atom it excites an electron and the atom heats up 5.when an electron falls back it releases a photo of a new energy level
21 of 31
....
6. this photon has less energy than before - energy was lost through heat 7.the phosphor then gives of white light - which we can see 8.manufacturers change the colour of light by using different combos of phosphors
22 of 31
wave particle duality
'all particles have a wave nature' Y=h/mv Y=h/p p-momentum DE BROGLIE WAVELENGTH
23 of 31
DIFFRACTION GRATING
a plate of glass or metal ruled with very close parallel lines, producing a spectrum by diffraction and interference of light.
24 of 31
electron diffraction
1.fired electrons at a crystal structure - which acted as a diffraction grating 3.producing areas of electrons and no electrons on the screen behind it 4.JUST LIKE the pattern when light diffracts
25 of 31
electron wavelength
change in p.d =eV eV=1/2mv^2 v=_/2eV/m Y=h/mv therefore,Y=h/_/2meV
26 of 31
WAVE-PARTICLE DUALITY
meaning particles sometimes behave like waves and wave sometimes behave like particles
27 of 31
e.g.1. light as a wave
diffraction, interference, plarisation and refraction
28 of 31
e.g.2. light as a particle
photoelectric effect - light behaves as a particle called a photon
29 of 31
e.g.3. electron as a particle
deflection by an electromagnetic field -- collisions with other particles
30 of 31
e.g.4. electron as a wave
electron diffraction
31 of 31

Other cards in this set

Card 2

Front

POLARIZATION

Back

Polarized light waves are light waves in which the vibrations occur in a single plane. e.g.

Card 3

Front

photoelectric effect

Back

Preview of the front of card 3

Card 4

Front

if light were a wave ...

Back

Preview of the front of card 4

Card 5

Front

THRESHOLD FREQUENCY

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Physics resources:

See all Physics resources »See all Quantum physics resources »