quantum physics threshold frequency

Hi guys, i am really struggled on how the photon model explains the threshold frequency?
Can someone explain it to me clearly.PLZ <3

Reply 1

phys981

Each photon must have enough energy (=workfunction) to release an electron. This minimum energy equates to a minimum frequency E=hf

If we think of waves, we could imagine the energy from a wave gradually building up until it reached the minimum needed to release an electron and this is not what is observed, therefore we need another way of understanding it.

The photon model, one photon -> one election explains why light of a certain frequency or above works, while light of lower frequency, no matter how intense, doesn't. (ie it doesn't matter how many photons you have, if they don't have a high enough energy, it doesn't work.

Reply 2

Kallisto

Entertainment Forum Helper

Original post by ayeshalarab

Hi guys, i am really struggled on how the photon model explains the threshold frequency?
Can someone explain it to me clearly.PLZ <3

Have you ever heard of the photoelectric effect by Albert Einstein? in this experiment he has shown that electrons on a specific cathode material in form of a metal plate (which holds the electrons in place) need a certain frequency to of light and thus a cartain (so called quantized) energy of photon that an electron comes off the metal plate. The least energy which is required to cause this effect is the work function. The energy which is below the work function would not cause this effect.

The experiment was performed for different materials as cathode (Na, Ag, Al, Li, etc.), with the result that the work function was always dfferent. That is to say every single element requires another quantized energy of the photon to stimulate an electron. As the energy of photons depends on the frequency of light, it means in turn that removing an electron from the surface of a cathode material depends on the frequency of light (particle).

Reply 3

ayeshalarab

thank you kallisto and phys981

Reply 4

ayeshalarab

thank you kallisto and phys981

Reply 5

Kallisto

Entertainment Forum Helper

Original post by ayeshalarab

thank you kallisto and phys981

It is a nice feeling to see that my reply was a true help for understanding.

Reply 6

ayeshalarab

I am doing revision for my upcoming test and it is really hard to understand with my teacher.

SO...I want to ask another question: " How do you explain threshold frequency in terms of photon model " :tongue:

I hope you can answer me soon if you see the msg.

P.S. I am really sorry if I disturb

Reply 7

Eimmanuel

Study Forum Helper

Original post by ayeshalarab

Hi guys, i am really struggled on how the photon model explains the threshold frequency?
Can someone explain it to me clearly.PLZ <3

Original post by ayeshalarab

I hope you can answer me soon if you see the msg.

P.S. I am really sorry if I disturb

I thought this question ("How do you explain threshold frequency in terms of photon model") is similar to the question (how the photon model explains the threshold frequency?) that you asked in the first post.

phys981 has explained what you needed. You may want to add the following

- Different metal has different work function.
- The work function of a metal is the minimum amount of energy required by an electron to escape its surface.
- Energy is needed to release the surface electrons because they are attracted by the electrostatic forces due to the positive metal ions.

PS: Understand the explanation NOT memorise the explanation.