## Threshold energy [ENDORSED]

Samantha Pacheco 2K
Posts: 60
Joined: Fri Sep 28, 2018 12:29 am

### Threshold energy

We went over an example that included threshold energy in the problem but what exactly is threshold energy of an electron and how does that factor into calculating the energy of a photon?

305008749
Posts: 31
Joined: Fri Sep 28, 2018 12:27 am

### Re: Threshold energy

From my understanding, threshold energy is the minimum amount of energy that is needed for a reaction to take place, so in this case the "reaction" is removing electrons.

Julia Lindner 1I
Posts: 35
Joined: Fri Sep 28, 2018 12:17 am

### Re: Threshold energy  [ENDORSED]

Threshold energy doesn't factor into calculating the energy per photon, but it does factor into calculating the kinetic energy, or the excess energy from the electron being ejected. The kinetic energy is equal to the energy of the incoming photon minus the threshold energy (energy required to eject the electron). As far as I know, Prof. Lavelle used work function and threshold energy interchangeably with regards to this equation.

mcredi
Posts: 63
Joined: Fri Sep 28, 2018 12:16 am

### Re: Threshold energy

Threshold energy is associated with the amount of energy required to remove an electron from a solid, like in the photoelectric effect, but is not used in the calculation of the energy of a photon

Milena Aragon 2B
Posts: 60
Joined: Fri Sep 28, 2018 12:19 am

### Re: Threshold energy

You also have to make sure that the energy of the photon exceeds that of the threshold energy in order to release an electron.

Kathryn Wilhem 1I
Posts: 60
Joined: Fri Sep 28, 2018 12:27 am

### Re: Threshold energy

When I went to a workshop the UA described the energy in the light like a glass of water. In the glass, the water is the energy needed to remove an electron, the threshold energy. The extra volume of the glass above the water is the kinetic energy that is given to the electron.

MichelleTran 1I
Posts: 40
Joined: Fri Sep 28, 2018 12:23 am

### Re: Threshold energy

Each atom has a minimum amount of energy needed for an electron to be released. That is the threshold amount of energy needed. Any energy more than that is excess and is given to the electron that is released. It is not used in calculating the energy of a photon.

Olivia Young 1A
Posts: 60
Joined: Fri Sep 28, 2018 12:24 am

### Re: Threshold energy

The threshold energy is the minimum amount of energy needed to eject an electron from a specific metal. The threshold energy is not used to calculate the energy of a photon, E=hv, but it is used in calculating the kinetic energy of the ejected electrons. The kinetic energy can be calculated by subtracting the threshold energy (work function) from the energy of the photon. If the energy of the photon isn't equal to the threshold energy, despite high intensity, then no electrons will eject, proving that light also has particle-like properties.

705088777
Posts: 37
Joined: Fri Sep 28, 2018 12:18 am

### Re: Threshold energy

Think of threshold as the minimum grade you need on a test to get an A in the class. That's what the UA described it as.

Manas Jinka
Posts: 32
Joined: Fri Sep 28, 2018 12:26 am

### Re: Threshold energy

The energy of the photon must be greater than the threshold energy in order to eject electrons and have them be detected.

JT Wechsler 2B
Posts: 62
Joined: Fri Sep 28, 2018 12:16 am

### Re: Threshold energy

The threshold energy is the minimum amount of energy that is required to remove an electron from the surface of the metal.

Emilee Hosking 1D
Posts: 32
Joined: Fri Sep 28, 2018 12:17 am

### Re: Threshold energy

From what I can tell, the threshold energy is the required energy to release an electron, but the actual energy of the photon can be more or less than the threshold energy. Correct me if I am wrong please.
So if the energy of the photon exceeds the threshold energy, will more electrons be emitted?

Nina Do 4L
Posts: 61
Joined: Fri Sep 28, 2018 12:27 am

### Re: Threshold energy

An electron will only be launched/ejected if the threshold energy is greater than or equal to the amount of work needed to do so.

Mallory_Podosin_1H
Posts: 31
Joined: Fri Sep 28, 2018 12:15 am

### Re: Threshold energy

Hi Samantha - Threshold energy has to do with the amount of energy required to release an electron from a metal. The threshold energy changes with whatever kind of metal you are using.

KHuang1L
Posts: 60
Joined: Fri Sep 28, 2018 12:19 am

### Re: Threshold energy

Threshold energy is basically the minimum energy required to remove an electron from an atom. The equation is energy from a photon = threshold energy + kinetic energy of the freed electron.

Posts: 73
Joined: Fri Sep 28, 2018 12:15 am

### Re: Threshold energy

I believe the threshold energy is also the work function kind of like how a wave function is essentially the same as an orbital

Anjali_Kumar1F
Posts: 62
Joined: Fri Sep 28, 2018 12:25 am

### Re: Threshold energy

whats is work function and how is it solved?

Andrew Bennecke
Posts: 62
Joined: Fri Sep 28, 2018 12:15 am

### Re: Threshold energy

The work function itself, or the values needed to calculate the kinetic energy and initial energy will be given. We are not expected to calculate the work function using the "complicated math".