Not a dumb question. They give you a pretty simple calculator, like that found on a Windows computer. I don't remember there being any exponent functions; only basic addition, subtraction, multiplication, and division. I don't think you'll see any questions on light physics. Check out the PCAT blueprint to see the list of tested topics
http://pcatweb.info/downloads/about/pcattestblueprintandsampleitems.pdf
Any questions with numbers in scientific notation will be simple and doable on scratch paper. You'll be expected to know how to divide and multiply them eg (5x10^-2) * (2x10^-2) = 1x10^-3