Longitudinal relativistic Doppler shift
For a light source and observer receding directly from each other at relative speed v, f_obs=f_source√[(1−v/c)/(1+v/c)].
Key knowledge
For a light source and observer receding directly from each other at relative speed v, f_obs=f_source√[(1−v/c)/(1+v/c)]. A signed v<0 gives direct approach and a blue shift; wavelength has the inverse factor.
Values and equations
f_obs=f_source√[(1−v/c)/(1+v/c)]
- f_obs,f_source
- Observed and source-rest frequencies Hz
- v,c
- Signed recession and light speeds m s⁻¹
Conditions and scope
- Vacuum light, inertial source and observer, collinear emission/reception, |v|<c.
- Transverse motion requires the angular formula. Cosmological and gravitational redshift cannot generally be assigned this flat-spacetime relative velocity.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
University Physics 3 §5.7: Longitudinal wavelength and frequency equations with signed recession convention; excludes applying the special-relativistic example to general cosmological distance inference.
2026-10-10 · Independent AI editorial review: All 136 unique authored Physics compact statements, all hypotheses and displayed equations/variable/units tables, all 192 Physics-origin semantic links, exact 165 author inspection matrix and mapped retained conceptual claims have been independently read. Three Physics-tagged Measurement realization records are delegated to root Measurement review. Scientific source verification combines exact author section inspection with independent whole compact-content/semantic review and targeted primary rechecks recorded below; it does not claim each full source body was independently reread. Independent AI editorial review is not human specialist certification or experimental replication. Field inventory is approved after independently reviewing the two added source-inspected band-construction methods. Receipt: physics-independent-content-inventory-review.1.
Entry details
Permanent link to this entry ↗- Record identity
- physics-relativistic-doppler
- Revision
- university-core.1
- Structured reference record
- University core expansion