Cathode Ray Tube
Before flat screens, every television was a cathode ray tube steering a beam of electrons onto a phosphor. This simulation shows the electron gun, the accelerating anode and the deflecting plates, letting you drive the glowing spot around the screen.
How to use this simulation
- Change the accelerating voltage
- Apply deflecting voltages to the vertical and horizontal plates
- Switch between electric and magnetic deflection
What to look for
- A higher accelerating voltage produces a faster beam that deflects less
- Electric deflection follows a parabolic path between the plates, then a straight line
- Magnetic deflection curves the beam perpendicular to both the field and the motion
The physics behind it
A heated cathode releases electrons by thermionic emission, and a potential difference V accelerates them to a kinetic energy eV. Charged plates then deflect the beam with an electric force, or coils deflect it magnetically. Because electrons have very little mass they respond almost instantly, which is what allowed the beam to scan a full picture many times a second.