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CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Frequency

The number of wave crests passing a point each second, symbol ν\nu, in Hz (s⁻¹). For light ν=c/λ\nu = c/\lambda, and the energy of each photon is E=hνE = h\nu, so higher frequency means more energetic photons.

The electromagnetic spectrumFrom left to right: gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves, radio waves. Wavelength increases to the right; frequency and photon energy increase to the left. Visible light spans about 400 nm (violet) to 700 nm (red).γ-rayX-rayUVIRmicrowaveradio400 nmvisible700 nmlonger wavelength →← higher frequency and photon energy

Frequency and photon energy rise toward the gamma-ray end.

Example

Green light at 500 nm has ν=2.998×108 m s−1500×10−9 m=6.00×1014\nu = \dfrac{2.998\times10^{8}\ \mathrm{m\,s^{-1}}}{500\times10^{-9}\ \mathrm{m}} = 6.00\times10^{14} Hz.

See alsoWavelengthPhotonPlanck's constant