As per what i learn that current(i) is rate at which charge flow through a cross section. Let assume we have 10 balls and it reaches another end while passing through some cross section, if 10 balls passes a cross section in 1 sec lets its current be i1 and if 10 balls passes a cross section in 0.1 sec lets its current be i2, so i2>i1

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I know about the stopping potential, and how does we reach saturation current(If even an electron with negligible velocity is attracted toward collector plate, this max possible current is saturation current and its directly proportional to intensity)

And after saturation limit, if we further increase potential difference between collector and emitter, so electron arrives at greater speed (and i also know that number of photoelectrons wont increase or decrease as frequency, Intensity is kept constant)

Now the question :

If we assume 10 photoelectron emitted by plate (at saturation limit) to reaches collector. If we assume a cross section to be collector plate, so that 10 photoelectron cross it in 1 sec(just assume) if potential difference is say V1 to have photocurrent i1

If we increase potential difference to have V2 so now 10 photoelectron crosses collector plate in 0.1 sec(it has more Kinetic energy and it reaches earlier than in former case) to have photocurrent i2

As if V2 > V1 implies i2 > i1 after saturation.

What did i miss there, i know i am wrong but cant figure out where?


1 Answer 1


Imagine buses are running between two cities. Everyday 10 buses start from A and reach B. So 'bus current' is 10 bus per day.

Suppose speed of all buses is doubled. The time of journey will be reduced. 'Bus current' will remain same. Seperation between buses will increase.

  • $\begingroup$ Would please elaborate a bit $\endgroup$
    – 5 Dots
    Apr 15 at 15:43
  • $\begingroup$ Think about this situation. 10 buses are leaving A every day. So 10 buses will reach B everyday. It does not matter how fast buses are moving. Unless more buses leave from A, 'bus current' will remain same! $\endgroup$ Apr 15 at 23:31
  • $\begingroup$ Where did i go gone? Is the definition of current is inappropriate? $\endgroup$
    – 5 Dots
    Apr 16 at 2:01
  • $\begingroup$ You have mixed up 'time of journey' with time in $i = q/t$. When speed of buses doubles, it is good news for passengers in bus. Their time of journey is going to be halved. But think from point of view a person sitting somewhere on route and watching the buses cross. This person will still observe same number of buses everyday. The buses would be going faster. Separation between buses will increase. But number of buses per day will remain same since number of buses leaving from A is same! $\endgroup$ Apr 17 at 14:06

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