Spectrophotometry and Beer-Lamberts Law

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SUMMARY

The discussion centers on calculating the wavelength and frequency of a molecule with a spectral line at 27319 cm-1. The correct approach to find the wavelength involves taking the reciprocal of the spectral line value and converting units appropriately. Frequency is determined using the formula: frequency = speed of the wave / wavelength, which confirms that frequency is not simply the reciprocal of wavelength. Participants clarified misconceptions regarding the relationship between frequency and wavelength, emphasizing the importance of unit consistency in calculations.

PREREQUISITES
  • Understanding of Beer-Lambert Law (A=εCl)
  • Familiarity with spectral lines and their significance in spectroscopy
  • Knowledge of wave properties, including wavelength and frequency
  • Basic unit conversion skills in physics
NEXT STEPS
  • Study the relationship between wavelength and frequency in wave mechanics
  • Explore the Beer-Lambert Law in detail, focusing on its applications in spectrophotometry
  • Learn about unit conversions in physics, particularly between different measurement systems
  • Investigate the concept of spectral lines and their role in molecular spectroscopy
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Chemistry students, physics learners, and professionals in analytical chemistry or spectroscopy who seek to deepen their understanding of spectrophotometry and the Beer-Lambert Law.

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Homework Statement


A molecule has a spectral line at 27319 cm-1

what is its wavelength?
what is its frequency?


Homework Equations


A=εCl
where A=absorbance, ε=molar extinction coefficient, C=concentration and l=path length

The Attempt at a Solution


thought about doing 1 over the spectral line for the wavelength, and correcting the units, but then realized frequency is 1 over the wavelength, which would just be the original answer

If I'm honest, i am not sure what it means by a spectral line, think the question may be badly worded
 
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Frequency is not 1/wavelength. It's easy to see that this equation is not true by looking at the units. Frequency has units of inverse time (e.g. s-1). Wavelength has units of distance (e.g. m). 1/wavelength does not give units of inverse time.

Frequency is (speed of the wave)/wavelength. You can check the units to see that dividing a speed by a distance give units of inverse time.
 

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