Fermat's principle of least time is only an approximation valid in the high-frequency limit

the verdict

SUPPORTED

the evidence backs this

Recorded sources

3 sources for · 0 against

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Is it true that Fermat's principle of least time is only an approximation valid in the high-frequency limit?

Yes. Fermat's principle of least time and related geometric optics formulations are well-known approximations that break down when wavelength or diffraction effects become non-negligible at lower frequencies.

Verdict: SUPPORTED · 3 sources for, 0 against · Last checked 31 Jul 2026

The analysis

The retrieved papers consistently support the principle that geometric optics (under which Fermat's principle of least time operates) is an approximation valid specifically in the high-frequency limit, whereas wave-optics and finite-frequency corrections dominate at lower frequencies.

Evidence for · 3

Gravitational Lensing from a Spacetime Perspective

2004

This paper reviews light propagation and spacetime perspectives where geometric optics and least time approximations are bounded by more general wave and geodesic descriptions.

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Perlick, V. (2004). Gravitational Lensing from a Spacetime Perspective. doi.org. https://doi.org/10.12942/lrr-2004-9

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More for · 2

Lensing of gravitational waves: Efficient wave-optics methods and validation with symmetric lenses

2023

This paper discusses how wave-optics effects become dominant at low frequencies, contrasting with the high-frequency geometric optics regime.

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Tambalo, G., Zumalacárregui, M., Dai, L., & Cheung, M. H. (2023). Lensing of gravitational waves: Efficient wave-optics methods and validation with symmetric lenses. doi.org. https://doi.org/10.1103/physrevd.108.043527

Propagation of polarized gravitational waves

2021

This paper notes that geometric optics approximations for wave propagation fail at large but finite frequencies, requiring wavelength-dependent corrections.

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Andersson, L., Joudioux, J., Oancea, M. A., & Raj, A. (2021). Propagation of polarized gravitational waves. doi.org. https://doi.org/10.1103/physrevd.103.044053

Related receipts

Is it true that Fermat's principle dictates that light follows paths of extremal time? SUPPORTED related question, same topic

What does the evidence say?

Receipt History

first checked31 Jul 2026

judged → SUPPORTED · 9231 Jul 2026

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