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I'm have a problem with photoelectric effect

it states that we have a wavelength of 2.08*10^-7 falls on the photosurface, a voltage of 1.40V is required to stop the emitted electrons from reaching the anode.

What is the largest wavelength of light which will result in emission of electrons from this photosurface.?

so we have the equation

eV=hf-W

W=h* critical frequency and

K=hf-W

and

f=speed of light/wavelength.

v=1.40

f=(3*10^8)/(2.08*10^-7)

And wouldn't the Kinetic energy be 0 for a wavelength of 2.08*10^-7

So i don't know where to go from here!! I want to do it but I can't it is frustrating!!

Any help is appreciation

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# Homework Help: Problem with photoelectric effect

**Physics Forums | Science Articles, Homework Help, Discussion**