Derivation of Beer-lambert's law

1. 11/4/2015
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2. 11/4/2015
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Introduction
Calculation
of Beer-
lambert’s
law
Conclusion
Outlines

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Absorption of
light

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Lambert’s Law

5. CONT…
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7. ABSORPTION COEFFICIENT
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8. TRANSMITTANCE
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8KlA
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9. OPACITY OF THE MEDIUM
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allowed to travel through medium.

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Beer’s law

11. thicknessl
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This equation is for Colorimetry
and spectrophotometry
BEER-LAMBERT’S LAW
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12.   (14)---log1loglog
eq;in theiprelstionshth).(and(T)and(A)betweeniprelationshThe
-(12)---log
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MOLAR ABSORPTIVITY
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13. MOLAR ABSORPTION COEFFICIENT
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cm.1iscellof
lenghtpathandmole/liter1of:concaforabsorptiontheasdefinedis
then,
cm1landmole/litre1CIf
eq.(14)fromtcoefficienabsorptionmolarofDefination
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Cl
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14. MIXTURE
(1) If the system containing several
substances.
each substance will contributes to rate of
absorption of light.
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-(15)---
.....
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lClCA
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15. DIFFERENCE
ABSORBANCE MOLAR ABSORBANCE
 It is extensive property.
 It change with change in
conc: and thickness.
 It varies with wavelenght
of incident light.
 It is intensive property.
 It remains constant,i.e
independent of conc and
thickness of vessel.
 Its value different at
different conc.
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έ

16. VALIDITY OF BEER’S LAW
 This law is valid for solution.
 Only strictly valid for single wavelength.
 Beer-lambert’s law valid for except when high
radiation beam are employed (Lasers).
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17. TESTING BEER-LAMBERT’S LAW
 We know,
Hence for give substance at give (l)
It means law is valid for straight line when
absorbance against conc:
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ClA 
CA

18. DEVIATION IN LAW
 Presence of impurities that fluorescence or
absorb at the absorbance wavelength .
 Deviation may if monochromatic light is not
used.
 Width of silt is not proper.
 Polymerization f impurities.
 Dissociation, ionization or association of the
solute in solution.
 Presence of trace amount foreign substance
in the solution.
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19. 1
• Determination of unknown
compound by using know.
2
• Measurement of absorbance of
the compound by using
spectrophotometer.
3
• To draw absorption spectra. To
record variation by change
wavelength of incident light.
Applications
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20. CONCLUSION
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we were able to see different
amounts of absorbency using the
law’s different analyte.
The calorimeter measured the
wavelengths of the ions to produce
the absorbency value.
A reference solution was also
created to help determine the
equilibrium constant for each
solution, and also is was used to
determine how precise our results
were.

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