# Y Intercept of photoelectric effect graph?

In a graph of KE=hf-W (the photoelectric effect equation), why is the work function equal to the y intercept? I mean I can see why it is using the equation (y=mx-c) but conceptually, why is the work function - the minimum energy required to cause emission of electrons - the y intercept of this graph?

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Couldn't you figure this out yourself? –  Ron Maimon Nov 7 '11 at 17:27

The equation requires that u have to give at least an energy equal to the wave function of the metal to eject an electron, if that condition is not met then nothing will happen,

so the work function is the EXTRAPOLATED INTERCEPT of the graph,

as it can be clearly seen that when f=0 , KE = -w , which is impossibe as KE cannot be negative,

so the graph never intersects the X axis, its only the extended or extrapolated graph(on which professors show with a dotted line) which intersects it.

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