Sec 2 - EM Radiation & Quantum Phenomena
The Photoelectric Effect: Cover Me
whats the frequency + WL of red light Lower Frequency + Long WL
whats the frequency + WL of blue light Higher Frequency + Shorter WL ( a wave carrying more energy has a large amplitude i think)
what does c = c = F x WL
whats the deal with Red Photons Red Photons = Less Energy
whats thed deal with Blue Photons Blue Photons = More Energy (more dangerous, like gamma rays)
what is 1 V = to 1 V is equal to 1 J / C
The Photoelectric Effect:
whats the deal witih how u can get a Metal to emit Es by shining a Light with a high enuf Freq. onto the surface of a Metal ( 'Light' means any EM Radiation not just Visible Light )
For most metals what Freq. does this fall into the UV range
1) whats the deal with what Free Es on the surface of the metal do Free Es on the Surface of the Metal abosrb En from the Light
2) what do the Es have to do to be released ( or emitted ) 2 if an E. absorbs enough En, the bonds holding it to the Metal break & the E. is released
3) Whats this effect called + what are the Es that are emitted called Photoelectric Efffect + Photoelectrons
When the F.......... of Light is above the T........... Freq., how is the no. of PhotoEs related to the Intensity of the Light Frequency Threshold they are directly Proportional
Three Main Conclusions were reached from experiments on the Photoelectric effect, u need to know em only not any exp. details :
Conc. 1: whats the deal with a Threshold Freq. For a given Metal, no PhotoEs are emitted if the radiation has a Freq. below a certain value ( the certain value = called the Threshold Freq. )
Conc. 2: Whats the deal with the what the PhotoEs are emitted with + ranging from what to what The PhotoEs = emitted with a variety of Kinetic Energies ranging from 0 to the Maximum Value
^^ What does this Value of Max. KE increase with + what is unaffected by ^ with Freq. of the Radiation + = Unaffected by the Intensity of the Radiation ( These 2 conclusions (this & 1 above) puzzled scientists cos they cant be explained using Wave Theory )
Conc. 3: what 2 things are Proprtional to each other in the Photoelectric effect ????? The no. of PhotoEs emitted per second is Proportional to the Intensity of the Radiation
The Photoelectric Effect cudnt = explained by W..... Theory Wave
According to Wave Theory:
1) For a particular Freq. of light, whats proportional to what the En carried is Proportional to the Intensity of the Beam
2) what would the En carried by the light be spread evenly over the Wavefront (whats a wavefront?)
3) whats the deal with each free E. on the surface of the metal & the incoming wave each free E. on the surface of the metal wud gain a bit of En from each incoming wave
4) what wud gradually happen to each E. each E. wud gain enuf En = to leave the Metal
So...the higher the i..... of the wave, the more e...... it shud transfer to each e........ - what shud the KE ^ with intensity Energy electron - the KE shud increase with intensity ( theres no explanation for the KE depending on the Freq. - unlike when it said above in conclusion 2 ) (the KE depends on the frequency which doesnt depend on the intensity i dont think)
There is also no explanation for the T....... Freq. , According to wave theory , the Es shud be emitted eventually no matter what the Freq. is Threshold
(but it cud = explained by Einsteins Photon Model of Light )
what did Einstein suggest about the EM waves ( & the En they carry ) that they exist in discrete packets of energy - Called Photons
Whats the formula for the En carried by One of these Photons (if some Qs are too easy = make em more challenging / vague) E = hf = hc / WL ( h = plancks constant , & c = speed of light in a vacuum )
Einstein saw these p..... of light as having a o....- o..- o...., particle-like Interaction with an Electron in a m...... surface Photons one-on-one Metal
^^ what wud a photon do ^^ A photon wud Transfer ALL its En to one, specific E.
According to the Photon Model :
1) When L..... hits its s......, the M..... is Bom...... by P...... Light surface Metal Bombarded Photons
2) what happen if one of these Photons c....... with a F.... Electron collides, the E. will gain En equal to hf ( the En the Photon is carrying )
What does an Electron need + why before it can leave the s....... of the m....... surface metal E. needs enuf En to break the bonds holding it there (or holding it to the Metal )
whats the name for this En called This En = called the Work Function
^^ + what does the value of the Work Function depend on depends on the Metal
( The Photon Model explains the Threshold Freq......... )
If the E.... gained by an E. (on the surface of the Metal) from a P...... is greater than the w..... f........, the E. = e......... Energy Photon work function emitted
whats the deal with If its isnt enuf En 2 If its isnt enuf En = the metal will heat up, but no Es will = emitted
Since, for Es to be released HF has to be more than or equal to Phi (the o with line down it), what mus the formula for the Threshold Freq be Since, for Es to be released HF has to be more than or equal to Phi (the o with line down it) the Threshold Freq must be f = Phi / h
( & the photon model explains the max. KE......... ) , the En transferred to an E. is HF ( its basically the same En the Photon is carrying to the E., since E = hf , the En. transferred to the E, is hf )
whats the deal with how you know what the KE is for the E. ( when it leaves the metal ofc) The KE the E. will = carrying when it LEAVES the metal is HF MINUS any En its lost on the way out (makes sense )
whats the deal with Es deeper down in the Metal they lose more En than the Es on the Surface (when theyre emitted) ( this explains the RANGE of Energies that can be seen when various Es leave )
Whats the minimum amount of En the E. can lose before its emitted ( ie whats that no. that it can go down ) The min. amount of En it can lose is the WORK FUNCTION
^^ KE of an emitted E. cant be greater than hf - phi
what does an electron below the surface need to do to reach the surface an electron below the surface needs to do work to reach the surface
The KE of the Es is I......... of the I...... ( the no. of P..... per second on an a.... ) , why is their KE independent of the Intensity Independent Intensity Photons Area, cos they can only absorb 1 Photon at a time
Increasing the i...... just means more photons per sec on an area - each Photon has the same e..... as before Intensity Energy
The max. KE can be measured using the idea of s........ potential stopping
The e...... Es are made to lose their En by doing w.... against an applied Pd (bit lost by this pd thing) emitted work
whats is the the stopping potential , Vs , The Vs is the Pd needed = stop the fastest moving Es, with Ek(max)
The w...... d..... by the Pd in s...... the f........ Es is equal to what exactly work done stopping fastest , to the En they were carrying ( the En the Es were carrying )
eVs = Ek(max) , what does e stand for + whats Ek(max) measured in e stands for the charge on the E. ( 1.6 x 10 to the -19) , Ek(max) = measured in Joules
what is V = V=W/Q (for when u have an electron in a circuit and need to work out work done or pd or smthn
how do u go from J to eV dividing by 1.6 x 10 to the -19
define electrvolt (find what it is & sirs eg of where it comes from, in ur book btw) the energy 1 electron has once its been accelerated thru a p.d of 1 volt
theres no time delay cos its an instant 1 on 1 particle like i......... interaction
Energy Levels & Photon Emission:
whats the deal with how Es in an Atom can only exist Es in an Atom can only exist in - Certain well-defined En levels
Each L..... is given a n........., whats the representation for the Ground State Level number n=1 represents the Ground State
what is the Ground State the lowest En state of an Atom
whats the deal with all Es ordinarily all Es are ordinarily at the ground state of an atom
whats the deal with each of the lines on a line spectra each of the lines on a line spectra is a specific En of photon thats been emitted
(some of the time nothing happens, some of teh time ionisation happens - E. collides with another E. in the atom & gives it so much En that the E. is removed from the atom, & sometimes = Excitation)
Whats the deal with how Es can Move Down En levels by emitting a Photon
whats the deal with the En of each photon emitted + why the En of each Photon Emitted can only take a certain allowed value + cos the transitions (of Es that emit photons to move En levels) are between definite En levels
^^So since these t....... are between d....... En levels, the En of each p...... emitted can only take a certain allowed v...... transitions definite photon value
( The energies involved = so tiny that it makes sense = use a more appropriate unit than the Joule, so the Electronvolt is used )
define Electronvolt (eV) the KE carried by an electron after it has been accelerated thru a P.d of 1 volt
En g...... by an E. (eV) = a......... voltage (V) (small formula) gained accelerating
how many joules are in 1 eV ( its prob given but idk ) 1eV = 1.60 x 10 to the -19 Joules
whats the En carried by each Photon equal to the difference in energies between two levels
Change in En. = E2 - E1 (their both small no.s) = hf = hc / wl (ie the Energy of the photon)
Es can also move u.. En levels, whats the deal with how they can move up a level 2 ways up, if they absorb a Photon with the Exact En Difference between the two levels + the electron in the atoms absorbs SOME of the En. from the Ek of the moving electron which causes the Excitation
whats the deal with when the E. exists in a higher En level its on average further away from the nucleus, but thats not a stable arrangement so it has to lose En & return to its ground state
whats the name for the movement of an E. to a higher En level Excitation ( opp. = de-excitation or relaxation i think )
( as it jumps down En levels, it has to give out En, it gives out that En in the form of a Photon, cos these are discrete or quanti fixed En levels, the En of photons given out as E moves between em = fixed )
if an E. is r....... from an a....., we say the atom is I......... removed Atom Ionised
The En of each En L..... within an a..... gives the amount En needed = remove an E. in that L..... from the Atom Level atom LEVEL
whats the deal with the Ionisation Energy the Ionisation Energy of an Atom is the amount of energy needed to completely remove an E. from the atom from the groun state (n=1)
why do we Es cascade down En levels cos with En levels close to each other theres many various way for VL photons of low en to be emmited (so the cascade down - in bigger or smaller jumps)
Fluorescent Tubes use Excited Es = Produce Light - gtt
what do F. tubes contain , across which , what is applied Mercury Vapour ( ie a bunch of Mercury Atoms ) , across which an initial High Voltage is applied
This high Voltage a.......... fast-moving free Es, what do these Free Es then do + what does this lead to accelerates, these accelerated fast-moving free Es IONISE some of the Mercury atoms , this produces more free Es ( cos Ionise means an E. is removed from the atom.....)
^^ When this f.... of f..... Es c..... with Es in Other M....... Atoms, What happens to the Es in those Mercury atoms flow free collides mercury , the Es in the Mercury Atoms are EXCITED to higher En levels
when these e...... Es then return to their g...... states (check vid) , what do they emit & in what range excited ground , they Emit Photons in the UV Range
what sort of coating (white powder) is there on the inside of the tube + what does this do Phosphor Coating on the inside of the tube, this absorbs these photons
theres a phosphor coating cos the UV photons emitted from the deexciting electrons in the mercury atoms are too high a frequency to be seen
The Es in the P........ atoms are then caused to go to much higher o..... ( cos they absorbed all those emitted photons from the M. atoms' Es ) Phosphor orbits
whats the deal with what happens to these Es after theyve gone to much higher orbits 2 these Es then Cascade down the En level, emitting many lower En photons in the form of Visible Light
what are the 2 things to know about the gas inside the tube gas = a t Lower Pressure + Gas = Partly Ionised
1) why is the gas at a lower pressure low pressure so that each E. can gain more En on avg per collission (remember as the E. travels across it gains Work Done for moving till it hits an E. and if ther too close not enough will go to each cos collissions will be too often)
^^ cos high pressure means more particles so it moves a short distance, gain a short amount of en, & then collides & gives it all away before repeating, so each E. doesnt get enuf En (this is to do with mercury atoms nd stuff in the fluoursecent tube) vice versa for low pressure
2) mercury vapour atoms = neutral objects, they got no charge & we dont really expect there to be free Es, so its a non-conductor = poor flow of electricity
^^ E. ionises thaty Atom & suddenly we got 2 Es & then go off down the tube causing further excitations or ionisations ??
^^so we need ionisation so that we have extra free moving Es & that allows the gas to conduct ???
why does it need to be partly ionised needs to be partly ionised so its conducting & theres free Es
if u S.... the light from a F. tube with a p.... ( or a diffraction grating, see pages 36 37 ), you get a line s....... split prism spectra
What is a Line Spectrum seen as is seen as a series of bright lines against a black background
what does Each Line correspond to Each line corresponds to a particular WL of light emitted by a source
Since only certain p.... e...... are allowed, u only see the W............ corresponding to these energies photon energies Wavelengths (WLs) ( all the others are there but pass thru cos they aint = right WL of photon En & so dont appear as a line that counts )
( Shining w...... light thru a cool g... gives an A......... Spectrum ) white gas Absorption
Continuous Spectra contain all possible w........... ) WLs
The spectrum of white light = continuous, if u split the light up with a p...., the c......... all m..... into each other - there arent any g.... in the spectrum prism colours merge gaps
H... things e..... a continuous s......... in the visble & i...... Hot emit spectrum infared
why are all the WLs allowed cos the Es arent confined to En levels in the object producing the continuous spectrum
When do u get a Line Absorption Spectrum when light with a continuous spectrum of En (white light) passes thru a cool gas
^^whats the deal with the gas being at a Low Temperature & the Es At Low Temperatures , most of the Es in the gas atoms will = in their ground states
^^The Es can only absorb p..... with e... equal to the d...... between two e..... levels photons energies difference energy
^^ P...... of the corresponding (the ones needed) W.......... are a...... by the Es to e...... them to higher e...... levels Photons WLs absorbed emit Energy
^^whats the deal with these WLs then ( the ones that got absorbed cos they = at the right En level for the Es to change En levels ) these WLs = then missing from the continuous spectrum when it comes out the other side of the gas
^^ So what do u then see after all the above ( once its passed thru the prism ) u see a continuous spectrum with black lines in it corresponding to the absorbed WLs ( see board )
If u compare the A......... & e....... spectra of a particular g..., the b..... lines in the absorption spectrum match up to the b.... lines in the emission spectrum Absorption Emission gas black bright ( so basically any other flippin colour ) ( see board )
Wave-Particle Duality:
What 2 things show Light as a Wave Interference & DIffraction
What does light produce Light produces Interference & Diffraction patterns - alternating bands of dark & light
These can Only be explained using W..... inferfering constructively ( when 2 waves overlap in phase) Or interfering destructively ( when the 2 waves are out of phase , pg 28 ) waves
whats one behaviour of Es as particles Deflection by Magnetic Field
What does the Photoelectric Effect show light behaving as as a Particle
Einstein explained the results of the Photoelectricity experiments ( first part of this sec ) by thinking of the beam of L...... as a series of particle-like p....... Light Photons
If a p...... of light is a Discrete bundle of En, then it can I....... with an E. in a one-to-one way photon Interact
De Brogile came up with the Wave-Particle Duality Theory : If a wave-like light showed particle properties (photons), particles like Es shud be expected to show wave-like properties
The De Brogile equation relates a wave property (WL) to a moving particle property (momentum, mv ) . h = plancks constant, whats the equation WL ( called the De Brogile WL ) = h / mv
The De Brogile Wave of a Particle can be interpreted as a ' P......... Wave ' Probability
( Many physicists at the time werent very impressed - his idea were just speculation, But later e.......... confirmed the wave nature of Es ) experiments
What shows the Wave nature of Es Electron Diffraction
When can Diffraction patterns be observed ( youll know what Diffraction is later on) when accelerated Es in a vaccum tube interact with the spaces in a graphite crystal
^^ This confrims that Es show wave-like properties
According to Wave Theory, whats the deal wiith the spread of lines in diffraction patterns the spread of lines in diffraction patterns Increases if the WL of the wave is greater
In E. diffraction experiments, a smaller accelerating voltage , ie slower Es , gives more widely-spaced rings
I....... the E. s..... ( & t/f the E. m......... ) & the d........ pattern circles s..... together towards the middle Increase speed momentum diffraction squash
^^ whats the deal with how this fits the De Brogile equation ( there was a Q' on page 21 , the 1st one idk why there was a some different unit thing....) it fits cos - If the Momentum is greater, the WL is shorter & the spread of the lines is smaller ( which is true cos if u look at his equation, theyre invesrely proportional, the WL & mv)
In general, W........... for Es accelerated in a Vaccum Tube is about the same size as EM waves in the x-ray part of the spectrum WL
If particles with a greater m..... ( eg Neutrons ) were travelling at the same s..... as the Es, they wud show a more tightly-packed d........ pattern mass speed diffraction
^^ Thats cos a Neutrons m..... ( & t/f its m....... ) is much greater than an Es, & soa N. has a s........ De Brogile WL mass momentum shorter
P...... dont show wave-like Properties all the time Particles
when do u only get Diffraction if a particle interacts with an object of about the same size as its De Brogile WL
The Photoelectric Effect: Cover Me
whats the frequency + WL of red light Lower Frequency + Long WL
whats the frequency + WL of blue light Higher Frequency + Shorter WL ( a wave carrying more energy has a large amplitude i think)
what does c = c = F x WL
whats the deal with Red Photons Red Photons = Less Energy
whats thed deal with Blue Photons Blue Photons = More Energy (more dangerous, like gamma rays)
what is 1 V = to 1 V is equal to 1 J / C
The Photoelectric Effect:
whats the deal witih how u can get a Metal to emit Es by shining a Light with a high enuf Freq. onto the surface of a Metal ( 'Light' means any EM Radiation not just Visible Light )
For most metals what Freq. does this fall into the UV range
1) whats the deal with what Free Es on the surface of the metal do Free Es on the Surface of the Metal abosrb En from the Light
2) what do the Es have to do to be released ( or emitted ) 2 if an E. absorbs enough En, the bonds holding it to the Metal break & the E. is released
3) Whats this effect called + what are the Es that are emitted called Photoelectric Efffect + Photoelectrons
When the F.......... of Light is above the T........... Freq., how is the no. of PhotoEs related to the Intensity of the Light Frequency Threshold they are directly Proportional
Three Main Conclusions were reached from experiments on the Photoelectric effect, u need to know em only not any exp. details :
Conc. 1: whats the deal with a Threshold Freq. For a given Metal, no PhotoEs are emitted if the radiation has a Freq. below a certain value ( the certain value = called the Threshold Freq. )
Conc. 2: Whats the deal with the what the PhotoEs are emitted with + ranging from what to what The PhotoEs = emitted with a variety of Kinetic Energies ranging from 0 to the Maximum Value
^^ What does this Value of Max. KE increase with + what is unaffected by ^ with Freq. of the Radiation + = Unaffected by the Intensity of the Radiation ( These 2 conclusions (this & 1 above) puzzled scientists cos they cant be explained using Wave Theory )
Conc. 3: what 2 things are Proprtional to each other in the Photoelectric effect ????? The no. of PhotoEs emitted per second is Proportional to the Intensity of the Radiation
The Photoelectric Effect cudnt = explained by W..... Theory Wave
According to Wave Theory:
1) For a particular Freq. of light, whats proportional to what the En carried is Proportional to the Intensity of the Beam
2) what would the En carried by the light be spread evenly over the Wavefront (whats a wavefront?)
3) whats the deal with each free E. on the surface of the metal & the incoming wave each free E. on the surface of the metal wud gain a bit of En from each incoming wave
4) what wud gradually happen to each E. each E. wud gain enuf En = to leave the Metal
So...the higher the i..... of the wave, the more e...... it shud transfer to each e........ - what shud the KE ^ with intensity Energy electron - the KE shud increase with intensity ( theres no explanation for the KE depending on the Freq. - unlike when it said above in conclusion 2 ) (the KE depends on the frequency which doesnt depend on the intensity i dont think)
There is also no explanation for the T....... Freq. , According to wave theory , the Es shud be emitted eventually no matter what the Freq. is Threshold
(but it cud = explained by Einsteins Photon Model of Light )
what did Einstein suggest about the EM waves ( & the En they carry ) that they exist in discrete packets of energy - Called Photons
Whats the formula for the En carried by One of these Photons (if some Qs are too easy = make em more challenging / vague) E = hf = hc / WL ( h = plancks constant , & c = speed of light in a vacuum )
Einstein saw these p..... of light as having a o....- o..- o...., particle-like Interaction with an Electron in a m...... surface Photons one-on-one Metal
^^ what wud a photon do ^^ A photon wud Transfer ALL its En to one, specific E.
According to the Photon Model :
1) When L..... hits its s......, the M..... is Bom...... by P...... Light surface Metal Bombarded Photons
2) what happen if one of these Photons c....... with a F.... Electron collides, the E. will gain En equal to hf ( the En the Photon is carrying )
What does an Electron need + why before it can leave the s....... of the m....... surface metal E. needs enuf En to break the bonds holding it there (or holding it to the Metal )
whats the name for this En called This En = called the Work Function
^^ + what does the value of the Work Function depend on depends on the Metal
( The Photon Model explains the Threshold Freq......... )
If the E.... gained by an E. (on the surface of the Metal) from a P...... is greater than the w..... f........, the E. = e......... Energy Photon work function emitted
whats the deal with If its isnt enuf En 2 If its isnt enuf En = the metal will heat up, but no Es will = emitted
Since, for Es to be released HF has to be more than or equal to Phi (the o with line down it), what mus the formula for the Threshold Freq be Since, for Es to be released HF has to be more than or equal to Phi (the o with line down it) the Threshold Freq must be f = Phi / h
( & the photon model explains the max. KE......... ) , the En transferred to an E. is HF ( its basically the same En the Photon is carrying to the E., since E = hf , the En. transferred to the E, is hf )
whats the deal with how you know what the KE is for the E. ( when it leaves the metal ofc) The KE the E. will = carrying when it LEAVES the metal is HF MINUS any En its lost on the way out (makes sense )
whats the deal with Es deeper down in the Metal they lose more En than the Es on the Surface (when theyre emitted) ( this explains the RANGE of Energies that can be seen when various Es leave )
Whats the minimum amount of En the E. can lose before its emitted ( ie whats that no. that it can go down ) The min. amount of En it can lose is the WORK FUNCTION
^^ KE of an emitted E. cant be greater than hf - phi
what does an electron below the surface need to do to reach the surface an electron below the surface needs to do work to reach the surface
The KE of the Es is I......... of the I...... ( the no. of P..... per second on an a.... ) , why is their KE independent of the Intensity Independent Intensity Photons Area, cos they can only absorb 1 Photon at a time
Increasing the i...... just means more photons per sec on an area - each Photon has the same e..... as before Intensity Energy
The max. KE can be measured using the idea of s........ potential stopping
The e...... Es are made to lose their En by doing w.... against an applied Pd (bit lost by this pd thing) emitted work
whats is the the stopping potential , Vs , The Vs is the Pd needed = stop the fastest moving Es, with Ek(max)
The w...... d..... by the Pd in s...... the f........ Es is equal to what exactly work done stopping fastest , to the En they were carrying ( the En the Es were carrying )
eVs = Ek(max) , what does e stand for + whats Ek(max) measured in e stands for the charge on the E. ( 1.6 x 10 to the -19) , Ek(max) = measured in Joules
what is V = V=W/Q (for when u have an electron in a circuit and need to work out work done or pd or smthn
how do u go from J to eV dividing by 1.6 x 10 to the -19
define electrvolt (find what it is & sirs eg of where it comes from, in ur book btw) the energy 1 electron has once its been accelerated thru a p.d of 1 volt
theres no time delay cos its an instant 1 on 1 particle like i......... interaction
Energy Levels & Photon Emission:
whats the deal with how Es in an Atom can only exist Es in an Atom can only exist in - Certain well-defined En levels
Each L..... is given a n........., whats the representation for the Ground State Level number n=1 represents the Ground State
what is the Ground State the lowest En state of an Atom
whats the deal with all Es ordinarily all Es are ordinarily at the ground state of an atom
whats the deal with each of the lines on a line spectra each of the lines on a line spectra is a specific En of photon thats been emitted
(some of the time nothing happens, some of teh time ionisation happens - E. collides with another E. in the atom & gives it so much En that the E. is removed from the atom, & sometimes = Excitation)
Whats the deal with how Es can Move Down En levels by emitting a Photon
whats the deal with the En of each photon emitted + why the En of each Photon Emitted can only take a certain allowed value + cos the transitions (of Es that emit photons to move En levels) are between definite En levels
^^So since these t....... are between d....... En levels, the En of each p...... emitted can only take a certain allowed v...... transitions definite photon value
( The energies involved = so tiny that it makes sense = use a more appropriate unit than the Joule, so the Electronvolt is used )
define Electronvolt (eV) the KE carried by an electron after it has been accelerated thru a P.d of 1 volt
En g...... by an E. (eV) = a......... voltage (V) (small formula) gained accelerating
how many joules are in 1 eV ( its prob given but idk ) 1eV = 1.60 x 10 to the -19 Joules
whats the En carried by each Photon equal to the difference in energies between two levels
Change in En. = E2 - E1 (their both small no.s) = hf = hc / wl (ie the Energy of the photon)
Es can also move u.. En levels, whats the deal with how they can move up a level 2 ways up, if they absorb a Photon with the Exact En Difference between the two levels + the electron in the atoms absorbs SOME of the En. from the Ek of the moving electron which causes the Excitation
whats the deal with when the E. exists in a higher En level its on average further away from the nucleus, but thats not a stable arrangement so it has to lose En & return to its ground state
whats the name for the movement of an E. to a higher En level Excitation ( opp. = de-excitation or relaxation i think )
( as it jumps down En levels, it has to give out En, it gives out that En in the form of a Photon, cos these are discrete or quanti fixed En levels, the En of photons given out as E moves between em = fixed )
if an E. is r....... from an a....., we say the atom is I......... removed Atom Ionised
The En of each En L..... within an a..... gives the amount En needed = remove an E. in that L..... from the Atom Level atom LEVEL
whats the deal with the Ionisation Energy the Ionisation Energy of an Atom is the amount of energy needed to completely remove an E. from the atom from the groun state (n=1)
why do we Es cascade down En levels cos with En levels close to each other theres many various way for VL photons of low en to be emmited (so the cascade down - in bigger or smaller jumps)
Fluorescent Tubes use Excited Es = Produce Light - gtt
what do F. tubes contain , across which , what is applied Mercury Vapour ( ie a bunch of Mercury Atoms ) , across which an initial High Voltage is applied
This high Voltage a.......... fast-moving free Es, what do these Free Es then do + what does this lead to accelerates, these accelerated fast-moving free Es IONISE some of the Mercury atoms , this produces more free Es ( cos Ionise means an E. is removed from the atom.....)
^^ When this f.... of f..... Es c..... with Es in Other M....... Atoms, What happens to the Es in those Mercury atoms flow free collides mercury , the Es in the Mercury Atoms are EXCITED to higher En levels
when these e...... Es then return to their g...... states (check vid) , what do they emit & in what range excited ground , they Emit Photons in the UV Range
what sort of coating (white powder) is there on the inside of the tube + what does this do Phosphor Coating on the inside of the tube, this absorbs these photons
theres a phosphor coating cos the UV photons emitted from the deexciting electrons in the mercury atoms are too high a frequency to be seen
The Es in the P........ atoms are then caused to go to much higher o..... ( cos they absorbed all those emitted photons from the M. atoms' Es ) Phosphor orbits
whats the deal with what happens to these Es after theyve gone to much higher orbits 2 these Es then Cascade down the En level, emitting many lower En photons in the form of Visible Light
what are the 2 things to know about the gas inside the tube gas = a t Lower Pressure + Gas = Partly Ionised
1) why is the gas at a lower pressure low pressure so that each E. can gain more En on avg per collission (remember as the E. travels across it gains Work Done for moving till it hits an E. and if ther too close not enough will go to each cos collissions will be too often)
^^ cos high pressure means more particles so it moves a short distance, gain a short amount of en, & then collides & gives it all away before repeating, so each E. doesnt get enuf En (this is to do with mercury atoms nd stuff in the fluoursecent tube) vice versa for low pressure
2) mercury vapour atoms = neutral objects, they got no charge & we dont really expect there to be free Es, so its a non-conductor = poor flow of electricity
^^ E. ionises thaty Atom & suddenly we got 2 Es & then go off down the tube causing further excitations or ionisations ??
^^so we need ionisation so that we have extra free moving Es & that allows the gas to conduct ???
why does it need to be partly ionised needs to be partly ionised so its conducting & theres free Es
if u S.... the light from a F. tube with a p.... ( or a diffraction grating, see pages 36 37 ), you get a line s....... split prism spectra
What is a Line Spectrum seen as is seen as a series of bright lines against a black background
what does Each Line correspond to Each line corresponds to a particular WL of light emitted by a source
Since only certain p.... e...... are allowed, u only see the W............ corresponding to these energies photon energies Wavelengths (WLs) ( all the others are there but pass thru cos they aint = right WL of photon En & so dont appear as a line that counts )
( Shining w...... light thru a cool g... gives an A......... Spectrum ) white gas Absorption
Continuous Spectra contain all possible w........... ) WLs
The spectrum of white light = continuous, if u split the light up with a p...., the c......... all m..... into each other - there arent any g.... in the spectrum prism colours merge gaps
H... things e..... a continuous s......... in the visble & i...... Hot emit spectrum infared
why are all the WLs allowed cos the Es arent confined to En levels in the object producing the continuous spectrum
When do u get a Line Absorption Spectrum when light with a continuous spectrum of En (white light) passes thru a cool gas
^^whats the deal with the gas being at a Low Temperature & the Es At Low Temperatures , most of the Es in the gas atoms will = in their ground states
^^The Es can only absorb p..... with e... equal to the d...... between two e..... levels photons energies difference energy
^^ P...... of the corresponding (the ones needed) W.......... are a...... by the Es to e...... them to higher e...... levels Photons WLs absorbed emit Energy
^^whats the deal with these WLs then ( the ones that got absorbed cos they = at the right En level for the Es to change En levels ) these WLs = then missing from the continuous spectrum when it comes out the other side of the gas
^^ So what do u then see after all the above ( once its passed thru the prism ) u see a continuous spectrum with black lines in it corresponding to the absorbed WLs ( see board )
If u compare the A......... & e....... spectra of a particular g..., the b..... lines in the absorption spectrum match up to the b.... lines in the emission spectrum Absorption Emission gas black bright ( so basically any other flippin colour ) ( see board )
Wave-Particle Duality:
What 2 things show Light as a Wave Interference & DIffraction
What does light produce Light produces Interference & Diffraction patterns - alternating bands of dark & light
These can Only be explained using W..... inferfering constructively ( when 2 waves overlap in phase) Or interfering destructively ( when the 2 waves are out of phase , pg 28 ) waves
whats one behaviour of Es as particles Deflection by Magnetic Field
What does the Photoelectric Effect show light behaving as as a Particle
Einstein explained the results of the Photoelectricity experiments ( first part of this sec ) by thinking of the beam of L...... as a series of particle-like p....... Light Photons
If a p...... of light is a Discrete bundle of En, then it can I....... with an E. in a one-to-one way photon Interact
De Brogile came up with the Wave-Particle Duality Theory : If a wave-like light showed particle properties (photons), particles like Es shud be expected to show wave-like properties
The De Brogile equation relates a wave property (WL) to a moving particle property (momentum, mv ) . h = plancks constant, whats the equation WL ( called the De Brogile WL ) = h / mv
The De Brogile Wave of a Particle can be interpreted as a ' P......... Wave ' Probability
( Many physicists at the time werent very impressed - his idea were just speculation, But later e.......... confirmed the wave nature of Es ) experiments
What shows the Wave nature of Es Electron Diffraction
When can Diffraction patterns be observed ( youll know what Diffraction is later on) when accelerated Es in a vaccum tube interact with the spaces in a graphite crystal
^^ This confrims that Es show wave-like properties
According to Wave Theory, whats the deal wiith the spread of lines in diffraction patterns the spread of lines in diffraction patterns Increases if the WL of the wave is greater
In E. diffraction experiments, a smaller accelerating voltage , ie slower Es , gives more widely-spaced rings
I....... the E. s..... ( & t/f the E. m......... ) & the d........ pattern circles s..... together towards the middle Increase speed momentum diffraction squash
^^ whats the deal with how this fits the De Brogile equation ( there was a Q' on page 21 , the 1st one idk why there was a some different unit thing....) it fits cos - If the Momentum is greater, the WL is shorter & the spread of the lines is smaller ( which is true cos if u look at his equation, theyre invesrely proportional, the WL & mv)
In general, W........... for Es accelerated in a Vaccum Tube is about the same size as EM waves in the x-ray part of the spectrum WL
If particles with a greater m..... ( eg Neutrons ) were travelling at the same s..... as the Es, they wud show a more tightly-packed d........ pattern mass speed diffraction
^^ Thats cos a Neutrons m..... ( & t/f its m....... ) is much greater than an Es, & soa N. has a s........ De Brogile WL mass momentum shorter
P...... dont show wave-like Properties all the time Particles
when do u only get Diffraction if a particle interacts with an object of about the same size as its De Brogile WL
