Vocabulary: electron volt, frequency, photoelectric effect, photon, photon flux, voltage, wavelength, work function Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. Suppose you went bowling, but instead of a bowling ball you rolled a ping pong ball down the alley. What do you think would happen? 2. Suppose you rolled a lot of ping pong balls at the bowling pins. Do you think that would change the results of your experiment? Explain. Gizmo Warm-up The photoelectric effect occurs when tiny packets of light, called photons, knock electrons away from a metal surface. Only photons with enough energy are able to dislodge electrons. In the Photoelectric Effect Gizmo, check that the Wavelength is 500 nm, the Photon flux is 5 γ/ms, the Voltage is 0.0 volts, and Potassium is selected. Click Flash the light to send photons of light (green arrows) toward a metal plate encased in a vacuum tube. 1. The blue dots on the metal plate are electrons. What happens when the photons hit the electrons? 2. What happens when the electrons reach the light bulb? When electrons reach the light bulb they complete a circuit, causing the bulb to glow briefly.