Question

Can someone explain the STOPPING VOLTAGE to me, i understand what it is, just not how it works.
Thanks

Answer 1

If the frequency and the intensity of the incident radiation are kept constant, the photoelectric current increases gradually with an increase in positive potential on collector electrode until all the photoelectrons emitted are collected. The photoelectric current attains a saturation value and does not increase further for any increase in the positive potential....now it doesn't matter how much potential you increase ...current will be constant ..it is called as stopping potential.

Answer 2

Thats really helpful but just to clarify, the +ve potential on the collector is due to all the e-1's being ejected - yes-.
The photoelectric current is the current resulting from the electrons jumping from the collector electrode to the other electrode - yes-.
Could you possibly rephrase the second sentence, don't really understand.
Really apreciate the help...

Answer 3

second sentence states 'saturation' which means after a certain extent there will be no increment in the current ...doesn't matter how much you increase the potential difference ..

Answer 4

basically stopping potential is the potential beyond which there is no further increment in photo electric current ...current will attain a constant value

Answer 5

So how does working out the stopping voltage allow us to calculate a plancks constant/the work function of the material

Answer 6

Is the collector electrode a cathode or anode?

Answer 7

kinetic energy=1/2*m*v^2= charge * potential

Answer 8

where potential i have used is stopping potential

Answer 9

@Ghazi, I am afraid this is not the stopping potential. Stopping potential is a cut-off potential and therefore nothing to do with saturation. Stopping potential is the potential applied to the anode to prevent any electron from reaching it

Answer 10

Carlos, that sounds more familiar.

Answer 11

my serious apology ....it is the minimum negative potential given to plate at which the photoelectric current becomes zero is called stopping potential or cut off potential

Answer 12

Could you explain how this value can then be used...

Answer 13

well you have the relation between kinetic energy and work function so in that if you've to calculate work function you need kinetic energy and you can have kinetic energy from stopping potential.... K.E= h*f-work function where h is planck's constant

Answer 14

The relationship is :\[hf=eV_{stopping}+eV_{work}\]
1) If you calculate the stopping potential for several frequencies and extrapolate for f=0, then you can find the work potential of the metal (anode). In this case:\[V_{work}=-V_{stopping}\]
2) Once you know the Work Potential, you can determine Planck's constant as @ghazi has explained \[h=e(V_{stopping}+V_{work})/f\]