Faraday effect
physical law
The Faraday effect or Faraday rotation, sometimes referred to as the magneto-optic Faraday effect (MOFE), is a physical magneto-optical phenomenon. The Faraday effect causes a polarization rotation which is proportional to the projection of the magnetic field along the direction of the light propagation. Formally, it is a special case of gyroelectromagnetism obtained when the dielectric permittivity tensor is diagonal. This effect occurs in most optically transparent dielectric materials (including liquids) under the influence of magnetic fields.
Discovered by Michael Faraday in 1845, the Faraday effect was the first experimental evidence that light and electromagnetism are related. The theoretical basis of electromagnetic radiation (which includes visible light) was completed by James Clerk Maxwell in the 1860s.
The Faraday effect is caused by left and right circularly polarized waves propagating at slightly different speeds, a property known as optical rotation (or circular birefringence). Since a linear polarization can be decomposed into the superposition of two equal-amplitude circularly polarized components of opposite handedness and different phase, the effect of a relative phase shift, induced by the Faraday effect, is to rotate the orientation of a wave's linear polarization.
The Faraday effect has applications in measuring instruments. For instance, the Faraday effect has been used to measure optical rotatory power, for remote sensing of magnetic fields (such as fiber optic current sensors) and for magneto-optical imaging.
This brief starts where responsible research should: with the source description of “Faraday effect” as physical law. Everything that follows is an evidence route, not borrowed authority.
Why this record matters
The subject matters to the history & society register because the source frames it as physical law. Its deeper value depends on whether names, dates, institutions and citations support that framing.
The record creator and administrative purpose are central evidence, because official documentation reflects both action and institutional priorities. The source revision retrieved here is dated May 24, 2026. The linked authority identifier is Q848501. The Library of Congress control number is sh85047180. 1 of 1 selected statements include explicit references; 1 carry qualifiers and 0 use preferred rank. The first chronological checks are 1845.
Official terminology may obscure informal participation, dissent or communities documented only indirectly. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Compare institutional narratives with records created by participants and affected communities. Dates and formal titles are useful anchors, but not substitutes for context.
- Event chronology
- Institutional context
- Locating named record creators
Contemporary correspondence, government or organizational records, oral histories and cited historical scholarship.
Three-step research path
- Establish the record: confirm the title “Faraday effect”, its source revision and the description used here.
- Expand the search: follow Faraday effect primary sources, Faraday effect archive and Faraday research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Faraday effect”?
- Which voices are present, absent or mediated by the institution?
- Who created the surviving record, and for what administrative purpose?
Search terms from this dossier
This entry incorporates text from “Faraday effect” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.