How to Discuss the Photoelectric Effect

Albert Einstein, Maxwell Planck, Sir Isaac Newton and Heinrich Hertz were all discussing the photoelectric effect around the turn of the nineteenth century. The big question on their mind was whether light was a wave or whether it was a particle.

Instructions

1. Discuss light, electromagnetic radiation, as both wave and particle. In physics-chemistry lingo, it has wave-particle duality.

2. Know that the laws of classical physics explain things like speed, velocity, acceleration, force and heat in every day functions and interactions. But when things get very small, like the size of electrons, protons and neutrons, classical physics doesn't work so well. That is when physicists turn to quantum physics and quantum mechanics for answers. Quanta are very small particles, like photons of light, packets of energy.

3. Return to the topic of the photoelectric effect, the release of electrons from a metal when light of a certain frequency shines on it. Yes, light has a force of energy that will knock electrons right out of a piece of metal. The key here is that it depends on the frequency of the light, not the intensity.

4. Learn now what physicists mean by intensity versus frequency. The amplitude, the height, of a wave determines its intensity, which determines the brightness of dimness of visible light. The frequency is how fast or slow light hits an object.

5. Understand that different intensities (brightness or dimness) of light of the same frequency on metal will cause the release of the same number of electrons. It doesn't matter if the light is a dim blue light or a bright red light, for example.

6. Remember Planck was the one who first came up with the idea in his blackbody radiation experiments that quanta, photons and energy of light were chunks or particles. At the time, all the other scientists were saying that light was a wave. So, Planck thought he must be wrong; however, his idea of these packets of energy was the only way the math on his experiment came out right.

7. Recall also that Einstein years later applied Planck's revolutionary ideas to his own theory of the photoelectric effect, which won him the Nobel Prize in 1921.