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Physics
Radio waves and electromagnetic fields
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Move the source electron and observe propagating fields and receiver response; switch to Electromagnetic wave to explore E/B, wavelength and antenna orientation.
Both blue electrons move only in their own antennas. Drag the transmitter electron up and down to make a wave; the position slider supports the keyboard. The pink arrow is the source electron's acceleration, the amber arrow the force on the receiving electron. Drag empty space to orbit. Vectors show field or force, not particle paths.
Preparing the 3D scene…
Radiation · t = 20.00 ns
Electric field E
Field display
- 1The source electron accelerates (a)
- 2Its electric field E spreads out at speed c
- 3After d/c, the force F = −eE drives the receiving electron
- Travel time d/c
- 30.02 ns
- Receiver E (relative)
- 0.00
- Receiving electron position
- 0.00
Electron motion is magnified and vectors compressed; the receiver is an illustrative oscillator, not a voltage reading.
Model notes
- Transmit and receive mode: the source electron follows a damped drive; displacement is in mm and magnified visually. The amplitude control sets drive amplitude, not the exact electron-motion amplitude. Speeds stay below 0.01c in the parameter range.
- Only the 1/r radiation component of an accelerated charge is drawn; near-field components are omitted. The field uses acceleration at retarded time t−r/c. Vectors are not electron paths; force on a negative electron is opposite E. The relative field scale compresses arrow lengths to fit the scene.
- The receiving electron is an illustrative driven oscillator with restoring force and damping, using relative displacement units. Graphs show position over time, not calibrated field, voltage or current. Receiver response depends on inertia; it does not simply copy source motion.
- Electrostatic configurations are a separate comparison: the electron is held stationary, time is paused, and dragging selects another fixed position. This magnified view has its own scale; it does not describe the total field of a moving charge or instantaneous signal transmission.
- This is a linearly polarized plane wave in vacuum: E ⟂ B ⟂ propagation, E and B are in phase, E/B = c and λ = c/f. The antennas represent a source and a probe, not a solution of a real antenna’s near field.
- In Electromagnetic wave mode, the plane-wave model omits distance attenuation, reflection, diffraction, resonance and receiver circuits. The field along the antenna is E cos θ, not a calibrated received voltage or power.
- One screen second corresponds to 10 simulated ns. Antenna sizes and vector lengths are illustrative; E and B use separate drawing scales. Coloured ribbons join vector tips; they are not moving matter or thick physical wave sheets.
- Source changes propagate at c; emitted waves continue after switching off. Electromagnetic wave mode uses a smooth 5 ns amplitude transition for visibility; actual antenna switching dynamics are not simulated.