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oned television is based around a CRT (cathode ray tube). The screen is coated on the inside surface with dots of chemicals called phosphors. When a beam of electrons hits a dot, the dot will glow. These phosphor dots are in groups of three: Red, Green, and Blue. This RGB system can then create all the other colours by combining what dots are illuminated. There are 3 signals that control the 3
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electron beams in the monitor, one for each RGB colour. Each beam only touches the dots that the signal tells it to light, a shadow mask blocking the path of the other beams. All the glowing dots together make the picture that you see, the human eye blending the dots to "see" all the different colours. This is then repeated for all the other pixels on the screen by scanning across the screen, in a row 1 pixel high, from left to right, dropping down and scanning back left.
Here we see a photo of a water droplet acting as a magnifying glass on a CRT screen. See how the three colours of dots create the overall pink.
1.2 What is an electron?
An electron is an elementary subatomic particle that carries an electrical charge of -1.6×10-19C. The properties of the electron have been determined by its interaction with other particles. The attractive Coulomb force between an electron and proton is what causes electrons to be bound into atoms. Current can be thought of as the flow of electrons within a conductor and is the rate of charge flow past a given point in an electric circuit, measured in Coulombs/second or Amperes. When an electron is in motion, it is deflected by external magnetic fields. When multiple electrons flow along a wire whilst in the presence of a magnetic field, the wire is deflected, giving rise to the concept of the electrical motor.
1.3 The charge/mass ratio
The charge/mass ratio is a physical quantity that is widely used to describe charged particles. But why do we single out charge and mass? We know from Newton’s Laws that acceleration is proportion to the force applied to an object and inversely proportional to the mass of the object.
and so where a is the acceleration, F is the force, and m is the mass.
We know that we can put forces on charged particles such as electrons by exposing them either to an electric field or a magnetic field, or even a combination of both. The force in both cases has been shown to be proportional to the charge on the particle. The key point is therefore that two particles with the same charge/mass ratio will move in the same path in a vacuum when subjected to the same electric and
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