Electromagnetic Waves
Watch a light wave travel: the electric field (orange) and magnetic field (teal) oscillate at 90° to each other, perfectly in phase, each one regenerating the other as the wave races forward at c.
Press Play to launch the wave. Turn on "Coupling lens" to freeze it and see where a changing E gives birth to B.
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They are in phase — both reach their maximum, zero, and minimum at the same instant and place. Their vectors are perpendicular in space, but there is zero time-phase difference between them. Students often confuse the 90° spatial angle with a 90° phase lag — they are different things.
A changing electric field produces a magnetic field (Ampère–Maxwell), and a changing magnetic field produces an electric field (Faraday). In a wave each one's change regenerates the other, so the disturbance sustains itself and travels forward without needing a medium.
Because the fields are each other's source. The oscillating E feeds B and the oscillating B feeds E, so the wave carries its own restoring mechanism through empty space — unlike sound, which needs particles to push.
Their ratio equals the speed of light: E₀/B₀ = c ≈ 3×10⁸ m/s. That's why the electric amplitude is numerically far larger than the magnetic one, even though both carry the wave equally.
Transverse. Both E and B oscillate perpendicular to the direction the wave travels (and perpendicular to each other). This is why EM waves can be polarized, unlike longitudinal sound waves.
Along the direction of E×B (the cross product). If E points up and B points sideways, the wave moves along the third mutually perpendicular axis — given by the right-hand rule.
Ek electromagnetic wave mein electric field (E) aur magnetic field (B) ke beech phase difference kitna hota hai?