Page 6 - Instrumental Analysis - Pharm D Clinical- 07-PA403

UV-visible Spectrophotometry

Wave properties of EMR

The wavelength and frequency of EMR are inversely proportional to
each other.

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Wave properties of EMR

3- Wavenumber (ῡ):

• It is the number of waves per centimeter. It is the reciprocal of
wavelength.

• The most common unit of wavenumber is cm–1

ῡ = 1/λ (waves/cm)

• Example: Calculate the wavenumber of an infrared radiation with a
wavelength of 5.00 μm.
λ = 5 μm = 5 x 10–4 cm
ῡ = 1/λ = 1 / (5 x 10–4) = 2000 cm–1

• Wavelength (λ) of sodium D line is 589 nm. What are the frequency
and wavenumber of this radiation?

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