F

Frequency

ν = c/λ; E = hν
Quick Reference
Formula / Notationν = c/λ; E = hν
Also Known AsWave frequency, ν, Hz, cycles per second, angular frequency ω (related)

What is Frequency?

The number of complete wave cycles per unit time, measured in hertz (Hz = cycles per second). For electromagnetic radiation, frequency is related to wavelength by c = λν, where c is the speed of light. Higher frequency radiation (UV, X-rays) carries more energy per photon.

Formula & Notation

ν = c/λ; E = hν

Other Names / Synonyms: Wave frequency, ν, Hz, cycles per second, angular frequency ω (related)

Properties & Characteristics

Frequency (ν) is the number of wave cycles passing a fixed point per unit time, measured in hertz (Hz = cycles per second). For electromagnetic radiation: E = hν = hc/λ (Planck-Einstein relation), where h = 6.626 × 10⁻³⁴ J·s. Frequency and wavelength are inversely proportional: ν = c/λ. In spectroscopy, wavenumber (ν̃ = 1/λ, in cm⁻¹) is commonly used in IR spectroscopy; NMR uses radiofrequency (MHz range).

Uses & Applications

Frequency is central to all spectroscopy: UV-Vis (10¹⁴–10¹⁵ Hz), IR (10¹²–10¹⁴ Hz), NMR (10⁷–10⁹ Hz), microwave (10⁹–10¹² Hz). Photon energy (E = hν) determines its ability to cause photochemical reactions, ionise atoms, or excite molecular vibrations. Resonance frequencies identify functional groups in NMR and IR.

Safety Information

High-frequency (high-energy) radiation (UV, X-rays, gamma rays) is ionising and causes DNA damage, radiation burns, and cancer. Lower-frequency radiation (IR, microwave, radio waves) is non-ionising but can cause tissue heating at high intensity. Always use appropriate shielding for the frequency range employed.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Frequency
Formula ν = c/λ; E = hν
Synonyms Wave frequency, ν, Hz, cycles per second, angular frequency ω (related)

Frequently Asked Questions

The number of complete wave cycles per unit time, measured in hertz (Hz = cycles per second). For electromagnetic radiation, frequency is related to wavelength by c = λν, where c is the speed of light. Higher frequency radiation (UV, X-rays) carries more energy per photon.

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