A magnetic lens is a device for the focusing or deflection of moving charged particles, such as electrons or ions, by use of the magnetic Lorentz force. Its strength can often be varied by usage of electromagnets.
Magnetic lenses are used in diverse applications, from cathode ray tubes over electron microscopy to particle accelerators.
A deflection yoke is a kind of magnetic lens, used in cathode-ray tubes to scan the electron beam both vertically and horizontally over the whole screen.
In a CRT television, the electron beam is moved in a raster scan on the screen. By adjusting the strength of the beam current, the brightness of the light produced by the phosphor on the screen can be varied. The cathode ray tube allowed the development of all-electronic television.
View the full Wikipedia page for Deflection yokeElectron optics is a mathematical framework for the calculation of electron trajectories in the presence of electromagnetic fields. The term optics is used because magnetic and electrostatic lenses act upon a charged particle beam similarly to optical lenses upon a light beam.
Electron optics calculations are crucial for the design of electron microscopes and particle accelerators. In the paraxial approximation, trajectory calculations can be carried out using ray transfer matrix analysis.
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