Physics of light and magnetism rewritten after almost two centuries
About 180 years ago, an experiment revealed that light and electromagnetism are fundamentally connected, and new work now shows this link is even stronger than scientists long believed.
Faraday’s pioneering experiment
In 1845, physicist Michael Faraday carried out the first experiment that directly tied together light and electromagnetism.
He directed light through a piece of glass that contained boracic acid and lead oxide while the glass was placed inside a magnetic field.
Faraday observed that the emerging light was changed: its plane of polarisation had been rotated as it passed through the magnetised glass.
The Faraday effect
Light is an electromagnetic wave, and for roughly 180 years the so-called Faraday effect has been accepted as evidence that light and electromagnetism are linked.
According to the standard explanation, the combined interaction of the external magnetic field, the electric charges in the glass, and the electric part of the light wave causes the polarisation of the light to rotate.
The light wave effectively begins to oscillate in a different direction compared with its orientation before entering the material.
Traditional view of light’s magnetic part
Despite the electromagnetic nature of light, the magnetic component of the light wave has long been treated as having almost no influence on the Faraday effect.
This assumption became a common part of the way physicists described how light interacts with matter in this phenomenon.
New findings on light–matter interaction
Amir Capua and Benjamin Assouline at the Hebrew University of Jerusalem in Israel have challenged the long-held view that the magnetic part of light is negligible in this context.
Their work shows that the magnetic component of light can, in some situations, play a significant role in the Faraday effect and interact actively with materials.
Quote on the second part of light
“There is a second part of light that we now understand interacts with materials,” says Capua.
Dark photon theory reference
The article also alludes to a “dark photon” theory of light that aims to overturn a century of established physics, suggesting that even familiar phenomena like the Faraday effect may be reinterpreted in a broader theoretical framework.
Author’s summary
New experiments show that the magnetic component of light actively shapes the Faraday effect, forcing physicists to deepen a 180-year-old picture of how light and magnetism interact in matter.