A dipole antenna's radiation pattern follows the classic far-field formula, doughnut-shaped around its axis:
E(θ) ∝ cos((πL/λ)·cosθ) − cos(πL/λ)
──────────────────────────── , sinθ
λ = c / f
resonance when L ≈ λ/2, λ, 3λ/2, ...
Antenna engineers pick a physical length close to a multiple of half the wavelength so the current standing wave on the rod reinforces itself (resonance), maximizing radiated power for a given input. Off-resonance, more power reflects back toward the transmitter instead of radiating — exactly what real EM simulation software (like antenna design tools) computes automatically before a physical prototype is built.
- Radiation lobe / field particles toggle — switches between a smooth far-field intensity surface and individual photon-like wavefronts.
- Frequency — sets the wavelength; changes both the lobe shape and the standing-wave pattern along the rod.
- Antenna length — the strongest lever on resonance; watch the tuning-state indicator swing between resonant and detuned.
- Transmit power — scales the brightness/speed of the emitted field and the peak-gain readout.
This resonance-matching principle is exactly what electromagnetic simulation tools optimize for in real antenna, RF filter, and PCB trace design before committing to costly hardware fabrication.