1. The problem statement, all variables and given/known data If 5 percent of the power of a 100 W bulb is radiated in the visible spectrum, how many visible photons are radiated per second? 2. Relevant equations E=hf=hc/λ 3. The attempt at a solution I know how to solve this, I just wanted to make sure. I will take 5 W or J/s as the power of the visible light, and once you know the energy of the visible light's photon in Joules finding the photons/second is easy. I am wondering though if it would be better to present a range of photons per second since the visible spectrum is a range of frequencies/wavelengths, or an average. The question seems like it wants a single answer.