Before you read this, I suggest you read post 19.27. Schrödinger’s equation, above, describes the motion of a particle (like an electron) in terms of its wavefunction, ψ (post 18.10), and energy, E. Here ∇ is the Laplacian operator (post 19.12), m is the mass of the particle, h is Planck’s constant (post 19.19) and… Continue reading 19.28 Solving Schrödinger’s equation
Before you read this, I suggest you read posts 19.12 and 19.24. If you’ve heard of “Schrödinger’s cat”, and didn’t understand what it was about, I suggest that you forget it – it won’t help you to understand how quantum theory (post 16.2) is used to explain things. But Schrödinger’s equation is very important –… Continue reading 19.27 Schrödinger’s equation
Before you read this, I suggest you read post 19.24. The uncertainty principle is named after Werner Heisenberg (picture above), the German physicist who suggested it in 1927. Heisenberg was awarded the Nobel prize in Physics in 1932. He was the first director of the Max Planck Institute for Physics; the Max Planck Institutes are… Continue reading 19.26 Heisenberg’s uncertainty principle
Before you read this, I suggest you read posts 19.23 and 19.24. In post 19.23 we saw that electromagnetic waves (post 19.9) could behave as particles, called photons, and in post 19.24 that particles, like electrons, could behave as waves. People often try to imagine what these things are “really” like and then the first… Continue reading 19.25 Wave-particle duality
Before you read this, I suggest you read post 19.23. In post 19.23, I explained the idea that light could behave as a stream of particles, as well as being a wave. So, do particles (or any other objects) behave as waves? This question was explored by the French physicist Louis de Broglie in his… Continue reading 19.24 Electron waves
When light shines on some materials, mostly metals, electrons may be emitted. This effect is called the photoelectric effect and the electrons emitted are called photoelectrons. Presumably, light energy overcomes the energy that attracts the electrons to the atomic nuclei in the metal (post 16.29) and gives them kinetic energy (post 16.21). The moving electrons… Continue reading 19.23 Photoelectric effect and photons
Research that identifies other planets that may be capable of sustaining life sometimes leads to the suggestion that we may soon be communicating with alien life forms. Recently such a planet was identified that is 111 light years away from earth (https://www.bbc.com/news/science-environment-49648746). What is a light year? It is the distance that light travels in… Continue reading 19.22 Light years away
If you shine a laser pointer from air into a denser medium (like glass or water), the beam is bent – as shown in the picture above. This bending of light, as it passes from one medium to another, is called refraction. It’s easy to see refraction using a laser pointer because it produces a… Continue reading 19.21 Refraction
In post 19.9, I wrote that light and other forms of electromagnetic radiation, are propagated as waves. What is the evidence for this statement? In the picture above, water waves (blue) on the sea, meet the entrance to a harbour that is protected by walls (black). The walls prevent the waves from entering the harbour… Continue reading 19.20 Diffraction – light is propagated as waves
Before you read this, I suggest that you read post 19.9. We know that hot objects can emit electromagnetic radiation because sometimes they are “red hot”; then they emit red light – a form of electromagnetic radiation (post 19.9). The wavelength of emitted radiation shifts to shorter wavelengths (longer frequencies, post 19.9) as the temperature… Continue reading 19.19 Radiation of heat
