Exams Prep Master
Spectroscopy is the measurement of the absorption and emission of light and other radiation by materials. It comprises of separating light (or, more correctly, electromagnetic radiation) into its constituent wavelengths (a spectrum), similar to how a prism divides light into a rainbow of colours. Spectroscopy was originally defined as the study of how light interacts with matter as a function of wavelength. Any measurement of a quantity as a function of wavelength or frequency is now referred to as spectroscopy. Electromagnetic radiation from a source passes through a sample containing molecules of interest during a spectroscopy experiment, causing absorption or emission.
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Key Takeaways: Spectroscopy, light, absorption, emission, electromagnetic radiation, wavelength, theory of relativity, quantum electrodynamics
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What is Spectroscopy?
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Spectroscopy is the process of dividing light (or, more properly, electromagnetic radiation) into its constituent wavelengths (a spectrum), just like a prism divides light into a rainbow of colours. A spectrum, on the other hand, is more than a basic 'rainbow' of colours. Electrons in atoms and molecules have quantized energy levels, and electromagnetic radiation can only be received and emitted at specific wavelengths. As a result, spectra are dotted with 'lines' of absorption or emission rather than just uniform.
During absorption, the sample absorbs energy from the light source. The sample emits light during emission. Spectroscopy can be used to investigate how particles interact with one another as a function of their collision energy. In quantum mechanics, the theory of relativity, and quantum electrodynamics, spectroscopic analysis is crucial.
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Working Principle of Spectroscopy
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The fundamental idea shared by all spectroscopic techniques is to light an electromagnetic radiation beam onto a sample and examine how it reacts to such stimulation. Typically, the response is measured as a function of radiation wavelength.
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Types of Spectroscopies
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Spectroscopy is a large field that encompasses a variety of sub-disciplines and procedures, all of which require highly specialized equipment. Let's look at different types of spectroscopies with their properties and applications.
- Infrared (IR) Spectroscopy
Absorption of infrared radiation causes changes in molecular vibrations within molecules, and infrared spectroscopy is based on 'measurements' of how bonds vibrate. In molecules, atom size, bond length, and bond strength vary, hence the frequency at which a specific bond absorbs infrared radiation varies throughout a range of bonds and modes of vibration.
IR spectroscopy applications:
Infrared spectroscopy is a simple and dependable technique used for a variety of tests and quality control in both research and industry. It comes in handy in forensic science, both in criminal and civil matters. Spectrometers have shrunk in size and are now easily transportable, even for field testing. With the advancement of modern technologies, it is now possible to properly quantify samples in solution (water produces a broad absorbance across the range of interest, and thus renders the spectra unreadable without this new technology).
IR spectroscopy is mostly used to determine a material's chemical makeup.
- Ultraviolet-Visible (UV/Vis) Spectroscopy
Ultraviolet spectroscopy is a quantitative technique for determining how much light a chemical compound absorbs. This is done by comparing the intensity of light passing through a sample to the intensity of light passing through a blank or reference sample.
Applications:
- Traditional Chemistry
- Life Science
- Microbiology
- Food & Agriculture
- Material Science
- Optical Components
- Pharmaceutical Research
- Petro chemistry
- Cosmetic Industry
- Quality Control
- Raman Spectroscopy
Raman spectroscopy is a non-destructive chemical analysis technique that yields detailed information about chemical structure, phase and polymorph, crystallinity, and molecular interactions. It is based on light's interaction with chemical bonds within a substance.
Raman spectroscopy is used in solid-state physics to characterise materials, monitor temperature, and determine the crystallographic orientation of a sample. A solid material, like a single molecule, can be distinguished by distinctive phonon modes.
- Nuclear Magnetic Resonance (NMR) Spectroscopy
Nuclear magnetic resonance spectroscopy (NMR spectroscopy) or magnetic resonance spectroscopy (MRS) is a spectroscopic technique used to examine local magnetic fields around atomic nuclei.
The NMR principle normally involves three successive steps:
In a constant magnetic field, the alignment (polarisation) of the magnetic nuclear spins B0.
The disturbance of this nuclear spin alignment by a weak oscillating magnetic field, commonly referred to as a radio-frequency (RF) pulse.
The detection and analysis of electromagnetic waves generated by the sample's nuclei as a result of this disruption.
- FTIR Spectroscopy
Fourier transform infrared spectroscopy (FTIR) is a technique for obtaining an infrared spectrum of a solid, liquid, or gas's absorption or emission. At the same time, an FTIR spectrometer collects high-resolution spectral data over a wide spectral range.
Compounds such as compounded plastics, mixes, fillers, paints, rubbers, coatings, resins, and adhesives are swiftly and clearly identified using FTIR spectroscopy. It can be used throughout the product lifetime, including design, manufacturing, and failure analysis.
- X-Ray Spectroscopy
X-ray spectroscopy is a technique for detecting and measuring photons, or light particles, with wavelengths in the X-ray region of the electromagnetic spectrum. It is used to assist scientists in understanding an object's chemical and elemental properties.
Many distinct X-ray spectroscopy methods are utilised in many different fields of research and industry, including archaeology, astronomy, and engineering. These methods can be used separately or in combination to provide a more complete image of the material or object under consideration.
Application of Spectroscopy
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Spectroscopy has a variety of applications in medicine, physics, chemistry, and astronomy.
- One of the initial applications was for determining a sample's atomic structure.
- The next major application was in astronomy, where it was used to study the spectral emission lines of the sun and distant galaxies.
- Exploration of space
- Optical fibres are used to monitor the cure of composites.
- Using near infrared spectroscopy, estimate the exposure durations of weathered wood.
- Absorption spectroscopy in the visible and infrared spectrums is used to measure various chemicals in food samples.
- Determination of hazardous substances in blood samples
- X-ray fluorescence elemental analysis that is non-destructive.
- Investigation of electronic structure using various spectroscopes.
- Calculate the speed and velocity of a faraway object
- Determining a muscle's metabolic structure
- Monitoring the concentration of dissolved oxygen in freshwater and marine ecosystems
- Respiratory gas analysis in hospitals
- Spectroscopy allows the sex of an egg to be determined as it is developing.
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Things to Remember
- Spectroscopy is the measuring of materials' absorption and emission of light and other radiation.
- The basic principle behind all spectroscopic techniques is to shine an electromagnetic radiation beam onto a sample and observe how it responds to such stimulation.
- It is the process of breaking down light (or, more accurately, electromagnetic radiation) into its constituent wavelengths (a spectrum), much like a prism does with light to produce a rainbow of colours.
- Atomic absorption spectroscopy, atomic emission spectroscopy, and atomic fluorescence spectroscopy are the three primary forms of atomic spectroscopy.
- Spectroscopy is used in a multitude of fields, including medicine, physics, chemistry, and astronomy.
Previous Year Questions
- The radius of hydrogen atom in the ground state is 0.53A˚. The radius of Li2+ ion (at. no. = 3) in a similar state is...[NEET 1995]
- What is the maximum numbers of electrons that can be associated with the following set of quantum numbers? n = 3, l = 1 and m = -1….[NEET 2013]
- A 0.66kg ball is moving with a speed of 100m/s. The associated wavelength will be (h = 6.6 \times 10-34 \, Js)(h=6.6×10−34Js)..[NEET 2010]
- The electronic configuration of Cu (at.no. = 29) is...[NEET 1991]
- The order of filling of electrons in the orbitals of an atom will be..[NEET 1991]
- The maximum number of electrons, present in an orbit that is represented by azimuthal quantum number (l)=3, will be...[NEET 1991]
- In a given atom no two electrons can have the same values of all the four quantum numbers. This is called...[NEET 1991]
- The orientation of an atomic orbital is governed by….[NEET 2006]
- Given, the mass of electron is 9.11×10−31kg, Planck's constant is 6.626×10−34Js, the uncertainty involved in the measurement of velocity within a distance of 0.1A˚ is...[NEET 2006]
- If ionisation potential for hydrogen atom is 13.6 eV, then ionisation potential for He+ will be...[NEET 2003]
- If uncertainty in position and momentum are equal, then uncertainty in velocity is...[NEET 2008]
- Which value is closest to the wavelength in nanometers of a quantum of light with frequency of 8×1015s−1?..[NEET 2003]
- Which of the following sets of quantum number is not possible:..[NEET 2007]
- An ion has 18 electrons in the outermost shell, it is..[NEET 1990]
- The frequency of radiation emitted when the electron falls from n = 4 to n = 1 in a hydrogen atom will be (Given ionisation energy of H=2.18×1018Jatom−1 and h=6.625×10−34Js)...[NEET 2004]
Sample Questions
Ques. What is a Spectrometer? (3 marks)
Ans: A spectrometer is scientific equipment used to determine the wavelength of electromagnetic radiations by detecting and isolating the spectral components based on their physical phenomena. For molecular spectroscopy, the spectrometer is often employed. Radiation source, detection, and analysis equipment make up the majority of the spectrometer. Emission spectrometers are used to excite molecules in a sample to higher energy levels and then evaluate the radiation produced as the molecules return to their original state. Typically, absorption spectrometers will pass known wavelength radiations. As a result, variations in the wavelength of the radiation can be determined. Fourier-transform spectrometers work in a similar way as absorption spectrometers, but they use broadband radiation and a computer to do it.
Ques: Is Infrared Light Capable of Analysing All Materials? (3 marks)
Ans: Yes, infrared light can be used to investigate practically any material because it can be used to examine both inorganic and organic components. The object or material must absorb infrared radiation or be evaluated using infrared light as a minimum requirement. However, not all materials are created equal, as some substances, such as noble gases and metals, cannot be investigated directly using infrared radiation. IR spectroscopy, on the other hand, is a good way to get a lot of information on organic materials. Because it is such a versatile method, IR spectroscopy is widely employed in research and industry.
Ques: What exactly is a spectroscope? (2 marks)
Ans. A spectroscope is an instrument that measures the properties of light in a specific region of the electromagnetic spectrum. Optical spectroscope, spectrophotometer, and spectrograph are all terms used to describe a spectroscope. Typically, the spectrometer of a spectroscope will create spectral lines that may be used to detect light wavelengths and intensities.
Ques: Cite the difference between Spectrophotometry and Spectroscopy? (3 marks)
Ans: Spectrophotometry and spectroscopy may appear to be the same thing.
There is, however, a significant distinction between spectroscopy and spectrophotometry. Spectroscopy studies matter by measuring the intensity of light in each wavelength involved in light's interaction with matter, whereas spectrophotometry analyses matter by measuring the intensity of light in each wavelength involved in light's interaction with matter (absorbance, reflectance, transmittance).
As a result, spectrophotometry is based on spectroscopy and can be considered a spectroscopy application.
The absorbance, reflectance, and transmission of light by gases, liquids, and solids can all be measured using spectrophotometry programmes.
Ques: What is IR spectroscopy and how does it work? (4 marks)
Ans: The principle of IR spectroscopy is based on the emission, reflection, and, most importantly, absorption of infrared light, which causes a couple of vibrations to regenerate inside the molecule.
Infrared spectroscopy, commonly known as vibrational spectroscopy, is a type of IR spectroscopy.
The following are some key points to remember about this spectroscopy:
IR spectroscopy in action:
-When IR radiations are applied to any molecule, the molecule absorbs the radiations, causing rotational and transitional vibrations inside the molecule.
-IR radiation does not have enough energy to cause electronic transitions inside the molecule.
-Due to the absorption of light, there are primarily two types of vibrations noticed in the molecule, stretching and bending vibrations, and as a result of this absorption, the molecule will exhibit an IR spectrum.
And for the entire process, equipment known as an IR spectrometer is required, which contains photo conducting detectors in which the IR spectrum is detected.
IR spectroscopy's applications include:
-The structure of the treated molecule can be identified using IR spectroscopy.
-Because each functional group has its own characteristic vibrational frequency value, this spectroscopy can also be used to determine which functional group is present in the molecule.
Ques: What is spectroscopy, and how is the electromagnetic spectrum determined by it? (3 marks)
Ans: The study of the interaction of radiations with matter is referred to as spectroscopy. The energy contained in the radiations is emitted as the wave propagates. The frequency or wavelength of electromagnetic radiations is measured, and they all travel at the speed of light.
When matter emits or absorbs light, spectra are observed. It is said to emit radiation when an object acts as a source of radiation. When matter interacts with radiation from another source, the matter is said to absorb radiation. When radiation strikes materials, it can either be reflected or absorbed.
We can organise the radiations in increasing or decreasing order of wavelength or frequency by evaluating their spectra. As a result, we have an electromagnetic spectrum. In the electromagnetic spectrum, radio waves, microwaves, infrared waves, visible radiation, X rays, and gamma rays, for example, are grouped in increasing order of frequency. The presence of a functional group in a molecule can also be identified using this spectroscopy because each group has a unique vibrational frequency value.
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