• Congratulations to the Class of 2024 on your results!
    Let us know how you went here
    Got a question about your uni preferences? Ask us here

Dilemma on Einstein's contribution to quantum theory (1 Viewer)

QZP

Well-Known Member
Joined
Oct 7, 2013
Messages
839
Gender
Undisclosed
HSC
2014
Hi have some gaps in my understanding:

Dotpoint "Identify Einstein’s contribution to quantum theory and its relation to black body radiation"
Einstein's contribution to quantum theory -> Proposed that light is quantised (is it wrong to say this since Planck proposed it? Should I instead say Einstein extended this to say that light's energy can only be transferred in its entirety?) and thus able to explain the photoelectric effect and therefore provide support for quantum theory since classical physics could not explain the photoelectric effect
Relation to black body radiation -> Einstein's explanation stemmed from Plank's hypothesis of black body radiation (quantisation of absorbed/emitted energy)

Is this the complete story? That's my understanding

Also have a question from a past paper
"Summarise Einstein's explanation of the results of Planck's black-body radiation experiments (4)"
My confusion is that Einstein did not explain black body radiation but the photoelectric effect?!?
 
Last edited:

astroman

Well-Known Member
Joined
May 12, 2014
Messages
7,069
Location
Las Vegas
Gender
Male
HSC
2015
from Andrew Harvey notes - Under the classical wave model of light, emission of electrons (from photoelectric effect) is
independent of frequency, however the Quantum particle model of light said that emission was
frequency dependent. Below a certain frequency (the critical or threshold or cut-off frequency) no
electrons were emitted, regardless of the intensity of the light.
Einstein’s contribution to quantum theory was that he used Planck’s idea of quanta and named these
packets of energy as photons. The use of this to explain the photoelectric effect meant that light
could be considered to be both a wave or a particle (photon). Classical physics was unable to explain
the photoelectric effect using the wave model of light. However Einstein explained the photoelectric
effect by using Planck's idea of quanta. He assumed that light comes in little packets of energy he
called photons. He explained the photoelectric effect with the particle model of light.
Einstein said the intensity of light depends on the amount of photons, not the energy of
the photons.
Einstein’s contributions lead to the start of quantum mechanics.
 

photastic

Well-Known Member
Joined
Feb 11, 2013
Messages
1,848
Gender
Male
HSC
2014
You must always mention photons for einstein's contribution towards quantum physics. Don't forget that
 

QZP

Well-Known Member
Joined
Oct 7, 2013
Messages
839
Gender
Undisclosed
HSC
2014
Hertz didn't propose quantisation at all though.. that was Planck :) Einstein provided an explanation for Planck's postulates about the quantisation of energy
Yeah i got the names jumbled sorry! Anyway, I don't think Einstein explained Planck's hypothesis? He only expanded on it which then explained photoelectric effect
 

Fizzy_Cyst

Owner @ Sigma Science + Phys Goat
Joined
Jan 14, 2011
Messages
1,212
Location
Parramatta, NSW
Gender
Male
HSC
2001
Uni Grad
2005
Planck studied BBR curve and from this derived a formula which could explain the graph -- consequence of this equation was that the radiation absorbed or emitted by the walls of a blackbody is quantised. The energy of each quanta being proportional to its frequency (E=hf)
Remember, Planck saw it as nothing more than a mathematical trick which could be used to explain the graph, nothing more.
Einstein applied Planck's idea of quantisation to EMR itself, saying that EMR is made up of these quanta, again the energy of which is proportional to frequency. He used this to explain PE Effect, the existence of a threshold frequency, why intensity has no effect on emission or energy of emitted electrons (remember: all or nothing principle and 1-to-1 interactions).
The extension of Planck's hypothesis and the application of quanta to EMR to explain PE Effect brought some physical reality to what was previously, merely an empirical approach to the equation of a line which had no physical basis. This provides support for Planck's hypothesis.

Whenever you are asked about Einsteins contribution etc...

START WITH PLANCK

And Planck DID NOT propose that light is quantised
 
  • Like
Reactions: QZP

photastic

Well-Known Member
Joined
Feb 11, 2013
Messages
1,848
Gender
Male
HSC
2014
Planck studied BBR curve and from this derived a formula which could explain the graph -- consequence of this equation was that the radiation absorbed or emitted by the walls of a blackbody is quantised. The energy of each quanta being proportional to its frequency (E=hf)
Remember, Planck saw it as nothing more than a mathematical trick which could be used to explain the graph, nothing more.
Einstein applied Planck's idea of quantisation to EMR itself, saying that EMR is made up of these quanta, again the energy of which is proportional to frequency. He used this to explain PE Effect, the existence of a threshold frequency, why intensity has no effect on emission or energy of emitted electrons (remember: all or nothing principle and 1-to-1 interactions).
The extension of Planck's hypothesis and the application of quanta to EMR to explain PE Effect brought some physical reality to what was previously, merely an empirical approach to the equation of a line which had no physical basis. This provides support for Planck's hypothesis.

Whenever you are asked about Einsteins contribution etc...

START WITH PLANCK

And Planck DID NOT propose that light is quantised
Wow, last time when I looked at your website, it was red and black but now it looks great, lol
 

QZP

Well-Known Member
Joined
Oct 7, 2013
Messages
839
Gender
Undisclosed
HSC
2014
Thanks fizzy :) Cleared up a lot for me
 

phamtom44

Member
Joined
Sep 19, 2013
Messages
69
Gender
Male
HSC
N/A
Yep what Fizzy said, so:
- Planck's hypothesis: radiation emitted/absorbed by atoms in the walls of blackbodies are quantised -> he simply thought it was a maths trick
- Einstein took this and extended it to all light -> used it to explain photoelectric effect
ALSO
Einstein didn't like probability/chance associated with principles .e.g Heisenburg's Uncertainty principle -> "God does not play dice" and so he came up with many thought experiments to rigorously test aspects of quantum theory which turned out to be true.
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top