[Tin tức] Classroom Aid – Electron Charge

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In this first segment of our “How small is it” video book, we cover the microscopic world.
We start with optical microscopes and take a look at some of the things that you can see with light. We also cover light diffraction and show how it sets a limit on the size of objects we can see.
To understand how we can go further than light can take us by using electrons, we cover wave-particle duality. For that we cover particle momentum and wave interference. For a closer examination of waves, we show the famous Young Double Slit experiment that illustrates the wave nature of light. We also cover Airy Disks as a wave effect to further illustrate the limits of light microscopes. Then we go deeper into the nature of electromagnetic radiation. Here we show how it is the very nature of empty space with its permittivity and permeability that determines the speed of light in a vacuum.
For the particle nature of light, we cover Blackbody Radiation, the radiation catastrophe and how Planck solved the problem by showing that light is created in integer multiples of a constant now called Planck’s constant. We then cover Einstein’s photo-electric effect that showed that light was absorbed in the same multiples of light quanta. We now call these light quanta photons.
To reconcile these two views of light, we return to Young’s double slit experiment and fire photons one at a time. The interference pattern appears over time. We cover how Louis Broglie extended this wave-particle duality to include electrons and other particles, and calculated the Broglie wavelength. The conclusion is that objects interact at points like a particle, but travel through space as a wave.
We then dig a little deeper into the nature of an electron starting with J.J. Thompson’s discovery using a mass spectrometer. We then cover how Robert Milliken found the charge of a electron. With the electron’s mass and charge known, we calculate its wavelength and find it much smaller than an optical photon’s wavelength. This makes it ideal for breaking through the diffusion limit to see much smaller objects.
We end by covering how a scanning electron microscope works and using it to view very small things – down to a carbon atom!}