Photons, Work energy, electrodes

[orangecatdog1]

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In a certain photoelectric device, photons are designed to strike a small metal cathode causing ejection of electrons and thus useable electric current. During a test of the device, the energy of each photon is initially less than the work function of the metal. At that point, a steady increase in the frequency of photon collisions with the cathode will:

a. Increase the current produced

b. Decrease the current available

c. Have no effect on the current

d. Increase the current only if the work function exceeds the energy of each photon

 

[MolonLabe16]

Hey, I'll try to answer your question.

So photons of a certain energy are colliding with the cathode, ejecting electrons that will in turn create a current. A certain threshold frequency has to be attained by these photons before electrons can be ejected.

KE (electron) = hf (photon) - W

If the frequency of the incoming photon is increased gradually and surpasses the threshold frequency, a current will be produced, so we can eliminate B and C.

If we examine choice D, it says current will increase only if the work function exceeds the energy of the photon. This doesn't make sense given our equation; no electrons will be ejected if the energy of the photon is lower than the work function. We can eliminate D.

Which leaves us with A, which sounds most like the correct answer.

Hope this helped!