Page 7 - Instrumental Analysis - Pharm D Clinical- 07-PA403

UV-visible Spectrophotometry

Photon properties of EMR

Relation between energy and frequency

• It is more convenient to think of light as particles called photons. Each

photon carries the energy (E) (in joules) which equals hν where h is

Planck’s constant (6.63 x 10–34 J.s).
• We relate the energy of a single photon to its wavelength, frequency, and

wavenumber by the relations:

• Note that the wavenumber and frequency are directly proportional to the
photon energy. Wavelength is inversely proportional to energy.

• EMR with shorter wavelength provides photons of greater energy and more
powerful radiation. For example, UV radiation which contains shorter λ
carries more energy than visible light.

9

The Electromagnetic Spectrum

High frequency Low frequency
Short wavelength Long wavelength
High energy
Low energy

10

6