Please guide about the quantum mechanics

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Slearner
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HiSorry for the long post but I thought I should test my understanding of quantum mechanics. Please correct me and guide me about the missing points. please guide about the part you find easy to explain.1)Well, mechanics is the study of action of force on matter and motion, and quantum mechanics is the mechanics of subatomic particles. 2)The story started at the discovery of black body; the body absorbing and radiating almost all kind of radiation perfectly. They discovered that color and temperature are correlated. Change in color shifts towards the small wavelength and high frequency. But reaching the ultraviolet, the energy decreased instead of becoming infinite (here I'm confused why they thought energy will be infinite at that point?)According to the Planck's quantum theory, energy occur in discrete packets, so, the energy release at ultraviolet, as E directly proportional to f, so a high frequency packet will need a specific high amount of energy that couldn't be fulfilled. So only the low energy packets are taken in by black body. 3)Then there comes a phenomena of photoelectric effect; shining light on metal surface released electrons. according to the* classical theory, energy is directly proportional to intensity. So, that means if you've higher intensity, you can change the energy of released electrons but that doesn't happen only number of released electrons changes. But the energy changed when f is changed. That couldn't be explained by classical theory.(why?)4)The Bohr theory suggested that electron release energy when it move from higher energy level to the lower one, the orbits were of discrete energies, but why? And why the atomic spectra has dark and bright lines? Why electron don't collapse on positive nucleus?As jumping of electron from one orbit to the other cause energy quanta, so can we say quantization of energy or light depends on the matter? Or they're interdependent?The electron don't collapse as there's a lower limit to the energy below which electron can't go to collapse. But what about the electrostatic force? Why it didn't act on the electron? 5)How all these can be explained if energy is quanta? And how these explain that energy is quantized? There will be lots of mistakes. Writing this I realized my concept of quantum mechanics isn't clear. Please explain the points and missing details.Thanks
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lerjj
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(Original post by Slearner)
HiSorry for the long post but I thought I should test my understanding of quantum mechanics. Please correct me and guide me about the missing points. please guide about the part you find easy to explain.1)Well, mechanics is the study of action of force on matter and motion, and quantum mechanics is the mechanics of subatomic particles. 2)The story started at the discovery of black body; the body absorbing and radiating almost all kind of radiation perfectly. They discovered that color and temperature are correlated. Change in color shifts towards the small wavelength and high frequency. But reaching the ultraviolet, the energy decreased instead of becoming infinite (here I'm confused why they thought energy will be infinite at that point?)According to the Planck's quantum theory, energy occur in discrete packets, so, the energy release at ultraviolet, as E directly proportional to f, so a high frequency packet will need a specific high amount of energy that couldn't be fulfilled. So only the low energy packets are taken in by black body. 3)Then there comes a phenomena of photoelectric effect; shining light on metal surface released electrons. according to the* classical theory, energy is directly proportional to intensity. So, that means if you've higher intensity, you can change the energy of released electrons but that doesn't happen only number of released electrons changes. But the energy changed when f is changed. That couldn't be explained by classical theory.(why?)4)The Bohr theory suggested that electron release energy when it move from higher energy level to the lower one, the orbits were of discrete energies, but why? And why the atomic spectra has dark and bright lines? Why electron don't collapse on positive nucleus?As jumping of electron from one orbit to the other cause energy quanta, so can we say quantization of energy or light depends on the matter? Or they're interdependent?The electron don't collapse as there's a lower limit to the energy below which electron can't go to collapse. But what about the electrostatic force? Why it didn't act on the electron? 5)How all these can be explained if energy is quanta? And how these explain that energy is quantized? There will be lots of mistakes. Writing this I realized my concept of quantum mechanics isn't clear. Please explain the points and missing details.Thanks
For 2) I have no idea. I don't know much about the black body problem or it's solution

3) Classical EM theory should suggest that more intense light causes more current. It turned out that increasing the frequency would increase the current, and very intense low frequency light would have no effect. This is best explained by discrete particles of high energy. The classical approach can only talk about the energy of a wave.

4) Bohr's model is wrong iirc. The electrons are quantized because of the exclusion principle, but the don't orbit the nucleus like planets, because then they would give off EM radiation like you say and would ultimately collapse into the nucleus (bad).

Hope that helps. Was this covered in your physics classes or in a book you read? Just wondering.
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Stonebridge
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(Original post by lerjj)
3) Classical EM theory should suggest that more intense light causes more current. It turned out that increasing the frequency would increase the current, and very intense low frequency light would have no effect. This is best explained by discrete particles of high energy. The classical approach can only talk about the energy of a wave.
Not really.
The classical model would predict that increasing the brightness/intensity of the light would increase the energy striking the surface per second and thus should increase the kinetic energy of the ejected electrons. This doesn't happen.
Increasing the frequency of the incident light increased the maximum kinetic energy of the electrons. Increasing the intensity did increase the current, as according to the photoelectric model, this increases the number of incident photons per second and thus the number of collisions per second with electrons, which in turn increases the number of emitted electrons.
The classical model expresses the energy in a wave as a function of its amplitude. The photon model puts the energy as being proportional to the frequency of the radiation.
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(Original post by Stonebridge)
Not really.
The classical model would predict that increasing the brightness/intensity of the light would increase the energy striking the surface per second and thus should increase the kinetic energy of the ejected electrons. This doesn't happen.
Increasing the frequency of the incident light increased the maximum kinetic energy of the electrons. Increasing the intensity did increase the current, as according to the photoelectric model, this increases the number of incident photons per second and thus the number of collisions per second with electrons, which in turn increases the number of emitted electrons.
The classical model expresses the energy in a wave as a function of its amplitude. The photon model puts the energy as being proportional to the frequency of the radiation.
Woops.

Should have thought about that a bit more before answering. How do you directly measure maximum kinetic energy again?
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(Original post by lerjj)
Woops.

Should have thought about that a bit more before answering. How do you directly measure maximum kinetic energy again?
The standard way is to measure the "stopping" potential. That is, the applied negative potential that just stops the emitted electrons reaching the other electrode.
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