Electromagnetic (EM) waves are generated by the movement of electrons. In an electric circuit, visible light can be generated when electrons (a current) move through a lamp. Electric circuits can also generate infra-red waves (TV remote controls), microwaves (ovens), x-rays (medical scanners) and radio waves (aircraft ground-to-air communications). These different types of EM waves have … Continue reading Properties of EM Waves
Thermal Equilibrium
Any object that has a constant temperature is in a state of thermal equilibrium. This means the rate at which energy is transferred to the object is exactly equal to the rate at which energy is transferred from the object. In the context of electromagnetic radiation, we can state that the rate at which the … Continue reading Thermal Equilibrium
Telescopes in Space
Why do we put telescopes in space? The reason is not to get "closer" to the things we are trying to observe! Although the Earth's atmosphere extends much further, we generally think of space as starting about 100 km above the Earth's surface (see here for more details) and that's a tiny distance compared even … Continue reading Telescopes in Space
Sound: A Quick Recap
Sound is the most common example of a longitudinal wave (if you need a second example in an examination, mention seismic P waves from earthquakes). It is therefore important that you can describe and explain sound waves. This includes how the human ear works (in physics terms) and how microphones and loudspeakers link sound to … Continue reading Sound: A Quick Recap
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