Confusion with the Photoelectric Experiment

[Fruit Water]

I've always struggled with circuits and never got a firm handle (hence the very basic questions...please bear with me).
What I understand of Lenard's Experiment:
Light hits the emitter plate and some electrons fly off.
...lol yeah that's about it. Here is one major confusion that I have:
Not all the electrons make it to the collector plate and I've been told it's because of the voltage from the battery. I don't understand what it's doing at all. I've read that
E (of battery) = eV matches or is greater than KE and this stops the electrons from making it to the other side.
But why? Also somehow current is thrown to the mix with the ammeter and I can't figure out how it's all related.
One of my biggest struggles is everything is so compartmentalized in my brain. Like I recognize that voltage tells you how much E to get to a location and current is rate of flow but when it comes to application everything is just very confusing. Then it worsens when I remember current is the opposite of the direction of the flow of electrons and whatnot.
I'd be completely stoked to clear this up!
Appreciate any helpful replies!

 

[mfb]

Different electrons released from the metal have different energies. Some have enough energy to reach the other electrode, others do not (they fall back to the metal or get lost somewhere else). The higher the potential difference, the smaller the number of electrons with sufficient energy.

A classical analogy: Let everyone jump over a bar. If you set the bar low enough nearly everyone can do it, if you set the bar higher only some will make it, and if you set the bar too high no one can jump over it. The highest bar where still some people make it tells you the maximal height humans can jump.

 

[Fruit Water]

Thanks for the reply!
That analogy was helpful!
EDIT:
While I was writing the below I was trying to pin point what was bothering me about this and I think I got it:
E = KE + PE
if we want to find the max KE then shouldn't PE be 0? But doesn't the PE represent the stopping potential? How does this play to the equation?
---
If I may ask additional questions- What is the importance in the maximal height (in terms of the analogy)?
If E = KE then that would imply 0 PE and it'd be really easy for electrons to get to the other side as long as they passed the threshold frequency, right? I see that if it's greater than KE, we would have some PE so not all electrons will be able to go through. Am I saying something that makes sense?

 

[mfb]

E = KE + PE
if we want to find the max KE then shouldn't PE be 0? But doesn't the PE represent the stopping potential? How does this play to the equation?

E is the energy the electrons have left after hitting the electrode? In that case, to find the maximal KE you want E=0 so you have PE=-KE (and PE is what we can measure). The bar has to be set so high that the best high jumpers don't have space left above the bar.

What is the importance in the maximal height (in terms of the analogy)?

Maximal jumping height corresponds to maximal electron energy, and that's the interesting quantity.

If E = KE then that would imply 0 PE and it'd be really easy for electrons to get to the other side as long as they passed the threshold frequency, right?

Yes, but then you don't learn anything about the kinetic energy of the electrons. In principle you can use this setting to find the threshold frequency, but in practice that is not advisable.

 

[Fruit Water]

So in the equation
KE = hv + workfunction
does that imply PE = - (hv + workfunction) ?
I see...I was getting caught up thinking E was energy of the electron. Is the electrode the collector plate or the emitter plate?

 

[mfb]

So in the equation
KE = hv + workfunction

That is a different equation, and looks at the emission process, not at what happens to the electron outside.

Is the electrode the collector plate or the emitter plate?

I used "electrode" as the thing that captures electrons emitted elsewhere. You could call it collector plate, although the voltage is in the opposite direction compared to typical emitter/collector pairs.

 

[Leo1233783]

The main difference with quantum tunnelling is the number of electrons involved in the measure and the level of detection. With a greatest potentials difference but more electrons, an adapted detector can capture a signal.