What Is the Stopping Potential When Using a Cut-Off Frequency Filter?

[yaylee]

Homework Statement

Assume the same set-up to measure the stopping potential Vs through different filters. Suppose a filter allowed through only light of frequency fo (the cut-off frequency) or lower. In this case, what would the stopping potential be?
1) you cannot tell, since different electrons will escape with different speeds
2) you need no stopping potential because no electrons escape from the metal
3) greater than zero: electrons escape, and must be stopped from drifting to the anode
4) zero

Homework Equations

KE = hf - W
Also: if the cutoff frequency of the light is not reached, no electrons are emitted from the metal.

The Attempt at a Solution

With the reasoning above concerning cutoff frequency, I chose answer choice 2. However, this was marked incorrect.

Any suggestions or comments would be greatly appreciated! :)

 

[berkeman]

What does this mean? "Assume the same set-up"