A beam of blue light falls on the cathode of a photocell so that electrons are emitted. The blue beam is then replaced by a yellow one with the same intensity and electrons are also emitted. What would happen to each of the following physical quantities when the blue beam is replaced by the yellow beam?
K: Maximum KE of electrons emitted
I : The magnitude of photoelectric current
A. K increases, I uncahged
B. K decreases , I unchanged
C. K decreases, I increases
D. K decreases, I decreases
Photoelectric equation : KE(max)= hf - (work function)
h = planck constant, f = frequency of incident light, KE(max) = maximum KE of photoelectron
The Attempt at a Solution
Since yellow light is now used, frequency decreased --> so K decreases
Since Intensity is unchanged, current unchanged --> so I unchanged
so I chose B.
Correct Answer : C
Which part did I understand wrongly? Thanks !