Videos tagged physics
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PY106 pre-class video for session 39 - The Photoelectric effect
In this video, we go over the concepts underlying the photoelectric effect. It was for his explanation of the photoelectric effect that Albert Einstein was awarded the Nobel prize in Physics, in fact. What is it? When light illuminates a surface, it [...]is possible, at least sometimes, for the light to cause electrons to be emitted from that surface. This effect played an important role in the development of our understanding of light, being explained in terms not of light acting as a wave, but as light acting as packets of energy we call photons.
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PY106 pre-class video for session 38 - Special Relativity
This video serves as a quick introduction to special relativity. Instead of focusing on things that are different in different reference frames, the video focuses on the spacetime interval. The spacetime interval is a quantity that all observers, at [...]least in constant-velocity reference frames, agree on. We'll make use of the spacetime interval to do a sample problem, which has a bearing on relativistic effects such as time dilation, length contraction, and the twin paradox.
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PY106 pre-class video for session 36 - Diffraction
In this video, we discuss the idea of diffraction, which is the spreading out of a wave when it encounters an opening or an obstacle. We'll go over the equation for single-slit diffraction. We'll also talk some more about the history of our [...]understanding of light, in which diffraction played an important role.
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PY106 pre-class video for session 35 - Interference in two dimensions
In this video, we look at general characteristics of the interference pattern produced by two sources that are emitting identical waves. Such an interference pattern is produced by a laser illuminating two narrow slits (a double slit), and by two [...]speakers, emitting sound waves, connected to the same source. Understanding the pattern comes down to the path-length difference: if you stand at a particular location and measure the distance you are from each source, the path-length difference is the difference between those two distances. If the path-length difference is an integer number of wavelengths, constructive interference results. If the path-length difference is an integer number of wavelengths plus half a wavelength, destructive interference results.
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PY106 pre-class video for session 34 - The human eye and the camera
In this relatively brief video, we compare and contrast the human eye and the camera. Optically speaking, these two devices are actually very similar, with the biggest difference coming in the way the focusing is done.
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PY106 pre-class video for session 33 - Image formation by lenses
In this video, we go over the basics of image formation by lenses. We start by comparing and contrasting lenses and mirrors. We continue by going over the equations we use for lenses (these turn out to be the same as those for mirrors, aside from the [...]lensmaker's equation that gives the focal length of a lens). Finally, we discuss the process of drawing a ray diagram for a lens.
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PY106 pre-class video for session 32 - Refraction
In this video, we discuss the basics of refraction, which commonly refers to the change in direction a beam of light generally experiences when it passes from one medium to another. The reason for a change in direction is that the speed of light [...]depends on the medium, so the speed of the light usually changes when the light changes medium. In the video, we will define the index of refraction; talk about a simple model of refraction; and go over Snell's law, which is an equation we apply to refraction.
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PY106 pre-class video for session 27 - Radiation pressure
In this video, we discuss the energy and momentum carried by an electromagnetic wave. Regarding energy, we often talk about the intensity (power per unit area) associated with an electromagnetic wave. When we talk about momentum, we often talk about [...]radiation pressure - pressure associated, for instance, with a beam of light shining on an object. The video wraps up with some calculations related to solar sails, which are spacecraft that use radiation pressure for propulsion.
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PY106 pre-class video for session 25 - The interference of waves
In this video, we talk about the interference of waves, and look specifically at constructive and destructive interference. We also look at the fact that interference is all about superposition - the net result is simply the sum of the individual [...]waves. Finally, we end the video with a discussion of beats, which is a nice application of constructive and destructive interference.
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