The effect on a photocurrent of reducing the frequency of photons

[Pushoam]

Homework Statement

Homework Equations

The Attempt at a Solution

As frequency is decreased to threshold, no. of emitted electrons will remain same, but their maximum kinetic energy will decrease. So, the current should decrease slowly.

For frequency less than the threshold frequency, no electron will be emitted. So, the current should fall down to 0 at threshold frequency and for frequency less than threshold frequency.Option(c) meets the above two conditions. So, this should be the correct option. Right?

 

[gneill]

As frequency is decreased to threshold, no. of emitted electrons will remain same, but their maximum kinetic energy will decrease. So, the current should decrease slowly.

How does the kinetic energy relate to the current? How is current defined?

 

[Pushoam]

How does the kinetic energy relate to the current? How is current defined?

The number of emitted electrons per unit time is independent of frequency for f > f_th.
So, even if the kinetic energy of the electron increases when frequency is increased, the average no. of electrons pasing a cross -sectional area per unit time remains independent of frequency.
So, the current is independent of frequency.

Hence, the answer is option (c).
Right?
$I = \frac {kn}t$, where n is no. of photons touching the metal surface and k is the fraction of photons which eject electrons

 

[gneill]

The number of emitted electrons per unit time is independent of frequency for f > f_th.
So, even if the kinetic energy of the electron increases when frequency is increased, the average no. of electrons pasing a cross -sectional area per unit time remains independent of frequency.
So, the current is independent of frequency.

Yes!

Hence, the answer is option (c).
Right?
$I = \frac {kn}t$, where n is no. of photons touching the metal surface and k is the fraction of photons which eject electrons

Yup!