Photon energy and frequency
One photon's energy is proportional to its frequency.
Key knowledge
A photon of frequency f has energy E = hf. The frequency and energy refer to the same frame; intensity also depends on the number of photons and is not the energy of one photon.
Values and equations
E = hf
- E
- Energy of one photon J
- h
- Planck constant J s
- f
- Photon frequency Hz
Conditions and scope
- Applies to photon energy, not a generic particle's kinetic energy.
- A beam with a range of frequencies has a corresponding range of photon energies.
Sources · 3
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
- University Physics, volume 3: Photoelectric EffectSamuel J. Ling, Jeff Sanny and William Moebs / OpenStax, Rice UniversityTextbook chapter
- Meet the ConstantsNational Institute of Standards and Technology (NIST)Reference guide
- Dual Nature of Radiation and Matter · Physics (2026–27 reprint)National Council of Educational Research and Training (NCERT)Textbook chapter · PDF
Evidence and review
OpenStax 6.2, equation 6.13 and intensity distinction; NIST supplies Planck-constant SI value/unit context.
2026-10-10 · Photon frequency-energy relation only; no single-photon emission mechanism or complete quantum-state description is certified.
Foundational review
2026-10-10 · Fresh primary-source inspection of the complete compact record, including every statement, equation, quantity and material condition, followed by independent AI editorial review. This check does not certify all linked lessons or every passage of every cited publication.
Sources from other places
Agreement within this scope
A photon’s energy is h times frequency; changing intensity at fixed frequency changes photon number rather than energy per photon.
Energy and frequency must be evaluated in the same reference frame.
National Council of Educational Research and Training (NCERT)
- Dual Nature of Radiation and Matter · Physics (2026–27 reprint) IndiaEnglish
11.6–11.7, photon properties
- Dual Nature of Radiation and Matter · Physics (2026–27 reprint)
Entry details
Permanent link to this entry ↗- Record identity
- physics-photon-energy
- Revision
- core.1
- Structured reference record
- Essential core · first collection