Physicists have developed various experimental techniques to measure the velocity of electrons. One common method is based on the principle of electron deflection in electric and magnetic fields. Here's a simplified explanation of one such technique:
Electron Beam: A beam of electrons is generated using a suitable electron source, such as a heated filament or a photoemission process.
Electric Field: The electron beam is then passed through an electric field created by applying a voltage across two plates. The electric field exerts a force on the electrons, causing them to accelerate or decelerate.
Magnetic Field: After passing through the electric field, the electron beam enters a region with a known magnetic field. The magnetic field exerts a force perpendicular to the electron velocity, causing the electrons to move in a curved path.
Deflection Measurement: The curved path of the electron beam can be observed using a detector such as a fluorescent screen or a photographic plate. By measuring the extent of deflection, physicists can determine the curvature of the path and relate it to the electron's velocity.
Calibrating the Fields: To obtain an accurate measurement, the electric and magnetic fields can be adjusted until the electron beam follows a known trajectory. By comparing the known trajectory with the observed deflection, the velocity of the electrons can be determined.
It's important to note that this is just one example of an experimental technique, and there are other methods used in different contexts. Additionally, modern experimental setups often involve sophisticated equipment and detectors to enhance precision and accuracy.
These experimental techniques allow physicists to measure the velocity of electrons and other properties associated with their motion. By combining these measurements with other data, such as the electron's mass, kinetic energy can be calculated using the appropriate equations of classical or quantum mechanics.