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