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### Optical absorption in a semiconductor for $E<E_g$ [duplicate]

Quoting from Solid State Electronic Devices (by Ben G. Streetman and Sanjay Banerjee): A photon with energy less than $E_g$ is unable to excite an electron from the valence band to the conduction ...
109 views

### Photon absorption by a hydrogen atom : [duplicate]

How does the photon absorption takes place in a hydrogen? The classical mechanics shows the absorption of photonic energy resulting in the excitation of atom. Intuitively, a photon with frequency ...
46 views

### Excitation of an electron [duplicate]

What effect does a light ray cause on an electron to make it excited. How a electron absorb energy?
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### Why do photon only interact with atoms whose electronic orbitals are at very particular energies? [duplicate]

From https://www.sciencealert.com/physicists-made-a-new-part-matter-part-light-particle-with-a-shake-of-an-atom: Photons - those fundamental particles of light - have a slew of interesting ...
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### Atomic model - absorption [duplicate]

I have a question regarding the absorption of light in e.g. hydrogen atoms: I didn't quite understand how the electron knows that it can only absorb photons of the right energy. I thought that when ...
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### How does an electron know whether a photon is of correct energy states? [duplicate]

Since to become excited an electron in its ground state have to absorb a particular frequency of light otherwise they will just pass through each other, I'm thinking how can the electron measure the ...
3k views

### How does absorption of light by atoms and molecules work?

I found this question on a hobby science forum (mainly about chemistry) and found embarrassingly that I couldn't answer the question. A few searches along the lines of 'photons absorption' here on Ph....
1k views

### What evidence is there for quantum leaps?

I find this very strange that an electron can 'teleport' from one energy level to another. So what evidence suggests this?
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### What is the status of massless photons traveling through a medium?

Photons in vacuum have no proper time, and they are not considered as observers and not as reference frame. But what about photons travelling through matter? Their velocity is lower than light speed, ...