Quantum Stuff: Energy Levels Photoelectric effect

[wormboge]

This question comes from the Examkracker's quote, "When a photon collides with an electron, it can only bump that electron to another energy level if it's energy corresponds to the energy difference between rungs." So if 1.5 joules is necessary to bump the electron up to the next level, would 1.7 joules also do the job?

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[mk04447]

Ummm not sure how to answer this. If one match would burn your house down, could two also do the trick?

 

[sapientnarwhal]

Ummm not sure how to answer this. If one match would burn your house down, could two also do the trick?

Idk about that...

Op is referring to absorption of a photon.
For the sake of MCAT EM knowledge, we can assume ideal conditions (i.e. a single hydrogen atom) If 1.5 J are required to excite and electron, this photon energy corresponds to a specific photon frequency necessary to excite an electron from a lowerto higher energy level. A photon of 1.7 J would not result in excitation, as the electron cannot absorb a fraction of a photon.

@NextStepTutor_1 is this reasoning correct?

Of course this is does not always hold true in the actual world, but for the sake of the mcat - modified law of pragnanz: approach problem in simplest possible manner.



EDIT: photoelectric effect refers to the ejection of electrons. In this case yes, if 1 match does the trick, 2 will certainly do the trick. The difference bw the two is the speed at which the electron is ejected. (KE = hf - Φ). Idk if you were asking about the photoelectric effect (thread title), or absorption/excitation (question in thread).

 

[wormboge]

Idk about that...

Op is referring to absorption of a photon.
For the sake of MCAT EM knowledge, we can assume ideal conditions (i.e. a single hydrogen atom) If 1.5 J are required to excite and electron, this photon energy corresponds to a specific photon frequency necessary to excite an electron from a lowerto higher energy level. A photon of 1.7 J would not result in excitation, as the electron cannot absorb a fraction of a photon.

@NextStepTutor_1 is this reasoning correct?

Of course this is does not always hold true in the actual world, but for the sake of the mcat - modified law of pragnanz: approach problem in simplest possible manner.



EDIT: photoelectric effect refers to the ejection of electrons. In this case yes, if 1 match does the trick, 2 will certainly do the trick. The difference bw the two is the speed at which the electron is ejected. (KE = hf - Φ). Idk if you were asking about the photoelectric effect (thread title), or absorption/excitation (question in thread).

I think I was confusing them in my initial post, but now I am curious about my question in context of both the photoelectric effect and absorption/excitation. Thanks for pointing that out!

 

[pretty_positron]

This question comes from the Examkracker's quote, "When a photon collides with an electron, it can only bump that electron to another energy level if it's energy corresponds to the energy difference between rungs." So if 1.5 joules is necessary to bump the electron up to the next level, would 1.7 joules also do the job?

The answer is yes, and that excess energy goes towards the kinetic energy of the electron that is released.

 

[sapientnarwhal]

The answer is yes, and that excess energy goes towards the kinetic energy of the electron that is released.

For the photoelectric effect only tho?

 

[pretty_positron]

For the photoelectric effect only tho?

Yeah, the photoelectric effect is named after photons and electrons.

It's different from when an atom absorbs a photon and an electron is jumps up to an excited state.

It's the same thing in theory, but just requires an amount of energy that exceeds mere jumping to an excited state to actually leaving the atom entirely.

That's what the work function is - the electron's binding energy.