Table of Contents
Table of Contents
Introduction:
Wavelength, frequency, and wavenumber are three key concepts in understanding of fundamental ideas of analytical chemistry. In this article, looking at their definitions, units, calculations, and uses, we'll be exploring these basic terms.
I. Wavelength (λ):
A. Definition:
Wavelength (λ) is the distance between two successive points in a wave that are in phase, typically being measured from crest to crest or trough to trough.
B. Unit:
Its unit is the meter denoted by (m).
C. Formula:
• λ = c / f
where:
• λ = Wavelength (m)
• c = Speed of light in a vacuum (approximately 3.00 x 10^8 m/s)
• f = Frequency (Hz)
D. Application:
• Wavelength is important in various analytical techniques, such as spectroscopy, where it decides what kind of electromagnetic radiation is being examined.
II. Frequency (f):
A. Definition:
Frequency (f) is the number of wave cycles passing through a point in one second.
B. Unit:
The unit of frequency is the Hertz (Hz), that represents cycles per second.
C. Formula:
• f = c / λ
where:
• f = Frequency (Hz)
• c = Speed of light in a vacuum (approximately 3.00 x 10^8 m/s)
• λ = Wavelength (m)
D. Application:
Frequency is crucial in spectroscopy (U-Vis & IR), nuclear magnetic resonance (NMR), and so many other analytical techniques where the interaction of waves with matter is studied.
III. Wavenumber (ν):
A. Definition:
Wavenumber (ν) is the reciprocal of wavelength and represents the number of waves per unit length.
B. Unit:
The unit of wavenumber is reciprocal meters (cm⁻¹ or m⁻¹).
C. Formula:
• ν = 1 / λ
where:
• ν = Wavenumber (cm⁻¹ or m⁻¹)
• λ = Wavelength (m)
D. Application:
Wavenumber is usually used in spectroscopy (IR spectroscopy) to analyze chemical substances and find molecular vibrations.
Conclusion:
Having a deep Understanding of the principles of wavelength, frequency, and wavenumber in analytical chemistry is important for a lot of applications, which includes spectroscopy (UV-Visible & Infrared) and nuclear magnetic resonance (NMR). Wavenumber is the reciprocal of wavelength and has an inverse relationship to frequency. These essential ideas assist scientists in the analysis and interpretation of data using a variety of analytical methodologies, which advances the discipline.
Absorbance, Transmittance and Reflection:
The study of substances and their properties is done analytically, which frequently necessitates measuring how light interacts with matter. Absorbance, transmittance, and reflection are three crucial concepts in this situation. We will examine these concepts in this article, along with their definitions, units, calculations, and usefulness.
I. Absorbance (A):
A. Definition:
• Absorbance (A) is also called as optical density (OD)
• It is the quantity of light that is being absorbed by a solution.
B. Unit:
Absorbance is a dimensionless quantity.
C. Formula:
• A = -log10(T)
where:
• A = Absorbance
• T = Transmittance
D. Application:
Absorbance is widely used in spectrophotometry to quantify the concentration of a solute in a solution, based on the Beer-Lambert law.
II. Transmittance (T):
A. Definition:
Transmittance (T) represents the fraction of incident light that passes through a substance without being absorbed.
B. Unit:
Transmittance is expressed as a percentage (%).
C. Formula:
• T = (I/I₀) x 100%
where:
• T = Transmittance (%)
• I = Intensity of transmitted light
• I₀ = Intensity of incident light
D. Application:
Transmittance is crucial in spectroscopy and analytical chemistry to determine the transparency and concentration of a sample.
III. Reflection (R):
A. Definition:
Reflection (R) measures the amount of incident light that bounces off a surface without being absorbed or transmitted.
B. Unit:
Reflection is denoted in percentage terms (%).
C. Formula:
• R = (I_r/I₀) x 100%
where:
• R = Reflection (%)
• Ir = Intensity of reflected light
• I₀ = Intensity of incident light
D. Application:
Reflection is essential in analytical techniques like reflectance spectroscopy and surface analysis.
Conclusion:
Understanding absorbance, transmittance, and reflection is essential for analyzing how light interacts with compounds in analytical chemistry. While transmittance measures how much light gets through, absorption measures how much light is absorbed. Reflection is the measurement of light that bounces back off a surface. These ideas are crucial for a variety of tasks, such as figuring out solute concentrations and describing materials and surfaces. Analytical chemists get useful tools for their investigations and analyses by knowing these terminology.