So, I got the following question. http://imageshack.us/photo/my-images/528/problemsl.jpg This is figure 13.1. http://imageshack.us/photo/my-images/100/131lg.jpg C is the cathode material. S is the light. The voltage begins at A. The circuit carrying any current that makes it through the potential difference is everything else to the right. So I think, okay, to identify the cathode material I need the work function value. Not too hard. http://imageshack.us/photo/my-images/710/excelx.jpg Note the formula I used for row 3. http://imageshack.us/photo/my-images/4/attemptsolution.jpg What did I do wrong? Why am I... what? These answers don't make any sense to me. Thanks! edit Since the images aren't appearing, I just linked to them. Imageshack.