Light is incident on the surface of metallic sodium, whose work function is 2.3 eV. The maximum speed of the photoelectrons emitted by the surface is 1.26e6 m/s. What is the wavelength of the light? I first converted Work Function to Joules: 2.3eV x (1.6e-19 J / 1eV) = 3.68e-19 J The equation I know is: hf = KEmax + Work Function hf can also be written as: hc/lamda I thought I would substitute c w/ the 1.26e6 m/s and use KEmax as zero. My answer was 2.27e-9m and that is not correct. I used the following: f = Work Function / h = 5.55e14 Hz Then I used: lamda = v/f = 2.27e-9 m If I can't substitute v for c, then what am I looking for with v??? I have looked at this problem for 3 days w/ no new ideas. Anyone else have any? Thank you!!