Electromagnetic Spectrum and Spectroscopy
Overview
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation, from the lowest frequencies of radio waves to the highest frequencies of gamma rays. Spectroscopy is the study of the interaction of electromagnetic radiation with matter. By studying the way that matter absorbs, emits, or scatters electromagnetic radiation, we can learn about the structure, composition, and dynamics of matter.
Key Concepts
The electromagnetic spectrumis a continuous range of frequencies. Electromagnetic radiation can be characterized by its frequency, wavelength, or energy.
Absorption spectroscopymeasures the amount of light that is absorbed by a sample at a particular wavelength. Emission spectroscopy measures the amount of light that is emitted by a sample at a particular wavelength.
Scattering spectroscopy* measures the amount of light that is scattered by a sample at a particular wavelength.
Applications of Spectroscopy
Spectroscopy is a powerful tool that has applications in many fields of science and engineering, including:
Chemistry:Spectroscopy can be used to identify and characterize compounds, determine their structure, and study their reactions. Biology: Spectroscopy can be used to study the structure and function of biomolecules, such as proteins and DNA.
Medicine:Spectroscopy can be used to diagnose and treat diseases, such as cancer and heart disease. Materials science: Spectroscopy can be used to study the structure and properties of materials, such as metals, semiconductors, and polymers.
Summary
The electromagnetic spectrum and spectroscopy are fundamental tools for studying the structure, composition, and dynamics of matter. Spectroscopy has a wide range of applications in many fields of science and engineering.Experiment: Electromagnetic Spectrum and Spectroscopy
Objective
- To understand the electromagnetic spectrum and its relationship to spectroscopy.
- To use spectroscopy to identify and characterize unknown substances.
Materials
- Spectrophotometer
- Samples of known and unknown substances
- Cuvettes
- Distilled water
Procedure
- Prepare the spectrophotometer. Turn on the spectrophotometer and allow it to warm up according to the manufacturer's instructions.
- Prepare the samples. Dissolve each sample in distilled water to create a solution with a concentration of approximately 1%.
- Fill the cuvettes. Fill a cuvette with distilled water and place it in the reference cell of the spectrophotometer. Fill a second cuvette with the sample solution and place it in the sample cell.
- Run the scan. Select the appropriate wavelength range and scan speed for the sample. The spectrophotometer will produce a graph of absorbance versus wavelength.
- Identify the peaks. The peaks on the graph correspond to the absorption of light by the sample. The wavelength of each peak corresponds to the energy of the absorbed photon.
Results
The following table shows the absorbance spectra of the known and unknown samples:
Sample |
Wavelength (nm) |
Absorbance |
|---|
Water |
n/a |
0 |
Benzene |
254 |
0.5 |
Ethanol |
275 |
0.3 |
Unknown 1 |
265 |
0.4 |
Unknown 2 |
280 |
0.2 |
Discussion
The absorbance spectra of the known and unknown samples can be used to identify the samples and characterize their properties. The wavelength of the peak absorbance corresponds to the energy of the absorbed photon, which in turn corresponds to the electronic structure of the molecule. The intensity of the peak absorbance corresponds to the concentration of the sample.
In this experiment, the unknown samples were identified as benzene and ethanol. Benzene has a peak absorbance at 254 nm, which corresponds to the energy of the π→πtransition. Ethanol has a peak absorbance at 275 nm, which corresponds to the energy of the n→π transition.
Spectroscopy is a powerful tool for identifying and characterizing unknown substances. By measuring the absorbance of light by a sample at different wavelengths, it is possible to determine the electronic structure of the molecule and its concentration.