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An incident photon, $f=5.5\times 10^{14}\ Hz$, hits a metal with a work function of $2.8\ eV$.

Find the maximum kinetic energy of any photo-electrons (in Joules).

I'm confused exactly how to do this, because I keep getting a negative kinetic energy. I have gotten 2.3 eV for the photon's energy, ans I know the equation is $E_{\ in}$ - Work Function = $KE_{\ max}$, but 2.3-2.8 is a negative energy! What am I doing wrong?

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up vote 1 down vote accepted

You're not doing this wrong. As you know energy of each photon is $E = hf = 2.27eV$ so they can't produce any photoelectrons on a metal with work function greater than that.

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