[SOLVED] Photoelectric effect, retarding potential 1. The problem statement, all variables and given/known data If the photocurrent of a photocell is cut off by a retarding potential of 0.92 volts for monochromatic radiation of 2500 A (A with the little circle above it), what is the work function of the material. 2. Relevant equations My book and professor use different symbols so I am going to define the symbols I am using: Ø means retarding potential / stopping potential W means work function e Ø = hc/lambda - W hc = 1240 eV 3. The attempt at a solution radiance is invariant with lambda b/c monochromatic According to the graph of photocurrent i vs. anode voltage V, it is when V = -Ø that i goes to 0. I don't see where 2500A fits in, except that that must give me lambda so that I can solve for W in the equation above.