## Photon Absorption/Emission

H-Atom ($E_{n}=-\frac{hR}{n^{2}}$)

Natalie Nartz 4F
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Joined: Thu Jul 11, 2019 12:17 am

### Photon Absorption/Emission

Does absorption of a photon always lead to a later emission of a photon? If so, does this emitted photon have the same energy as the photon that was first absorbed?

Shivam Rana 1D
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Joined: Fri Aug 09, 2019 12:16 am

### Re: Photon Absorption/Emission

As far as I remember, the absorption of light leads to the excitation of an electron to a higher state, and as that electron falls, the emission of a photon. This is why the black bands on an absorption spectrum are the colored bands on the emission spectrum (ex. hydrogen). During the photoelectric effect, if I'm right, electrons are the only things emitted.

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### Re: Photon Absorption/Emission

Absorption of a photon will excite electrons to a higher energy level only if the photon contains enough energy to move electrons to energy levels beyond their ground state.

When the electrons drop back down to their ground state, a photon will be emitted.

Kassidy Ford 1I
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### Re: Photon Absorption/Emission

The photon will be absorbed, exciting the electron to a higher energy state, and then as the electron drops back down to the ground state the photon will be emitted again. The photon will have the same amount of energy as it is absorbed and as it leaves because of the law of conservation of energy

Sydney Myers 4I
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### Re: Photon Absorption/Emission

RoshniVarmaDis1K wrote:Absorption of a photon will excite electrons to a higher energy level only if the photon contains enough energy to move electrons to energy levels beyond their ground state.

When the electrons drop back down to their ground state, a photon will be emitted.

This isn't technically correct and is confusing two concepts. An electron must be hit by a photon with the EXACT amount of energy it takes to move between energy levels in order to move. If the energy is greater, the electron will not move. UNLESS the photon has enough energy to completely remove the electron from the atom. That's when the threshold energy comes into play and it doesn't matter how much energy the photon has, as long as it is larger than the work function (energy required to remove an electron).

Wendy 1E
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### Re: Photon Absorption/Emission

Absorption of a photon does always lead to a later emission of a photon. The emitted photon has the same energy as the photon that was first absorbed due to the law of conservation of energy.

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Joined: Fri Aug 30, 2019 12:18 am

### Re: Photon Absorption/Emission

Is there a sign difference between the energy emitted versus the energy absorbed even though they are the same value? Like is the energy emitted a negative value and the energy absorbed positive?

Veronica_Lubera_2A
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### Re: Photon Absorption/Emission

Delta E will have a negative value when the electron is emitted (decreased energy) and positive sign when the electron is absorbed (increased energy). Energy in itself is always a positive value.

Michelle Xie 2B
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Joined: Sat Aug 17, 2019 12:18 am

### Re: Photon Absorption/Emission

The photon will be emitted again once the electron falls back down from the excited level. The photon has to have the exact amount of energy needed in order for the electron to absorb it and move to a higher energy level.