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The carrier wave used by radio frequency (RF) transmissions doesn't carry much information itself. To include speech or data, another wave has to be superimposed on the carrier wave, thus changing the shape of the carrier wave. The process of doing so is called modulation. To transmit sound, the audio signal must first be converted into an electric signal, using a transducer. After conversion, it is used to modulate a carrier signal.

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Modulation is the process of encoding information in a transmitted signal, while demodulation is the process of extracting information from the transmitted signal. Many factors influence how faithfully the extracted information replicates the original input information. Electromagnetic interference can degrade signals and make the original signal impossible to extract. Demodulators typically include multiple stages of amplification and filtering in order to eliminate interference.

The working principle of Raman spectroscopy is based on the inelastic scattering of monochromatic light from a laser source which changes its frequency upon interaction with the material. Photons from the laser are absorbed by the samples and it is remitted with a frequency shift up or down in comparison to the original monochromatic frequency this is called the Raman effect. These shifts in the frequency provide information about the rotational, vibrational, and other low-frequency transitions in the molecules. This technique can be used in studying the materials like solid, liquid, and gaseous nature. In order to understand spectroscopy better, we should know the difference between Rayleigh scattering and Raman scattering. Rayleigh scattering: In this case, the energy of the molecules is unchanged after the interaction with the molecules. The energy and the wavelength of the scattered photons are equal to that of the incident photon. Hence the energy of the scattering particle is conserved this is called Rayleigh scattering. Raman scattering: In this case, the light is scattered by the molecule, and the oscillating electromagnetic field of a photon induces a polarisation of the molecular electron cloud causing the molecules to be in a higher energy state with the energy of a photon is transferred to the molecule. This can be considered as the formation of a very short-lived complex between the photons and molecules which is commonly called the virtual state of molecules. The virtual state is not stable, and the photon is remitted almost immediately as scattered light. The schematic representation of the Raman and Rayleigh scattering is shown in Fig-3. Fig-3 Raman scattering and Rayleigh scattering [3] Components of Raman spectrometer Laser source: The laser source is used for the excitation of the sample and resulting scattered light. Injection/rejection filter: The filter delivers the laser to the sample and allows the scattered Raman light to pass through to the spectrograph. Spectrograph: The spectrograph is used to divide the light into separated wavelengths and measure the light intensity at each wavelength. Microscope: The microscope is used to focus the laser light onto a point on the sample surface and collects the Raman light. Computer: It provides instrumental control and data handling and manipulation. Fig-4 Schematic representation of Raman spectrometer with its components [4] Information from Raman spectroscopy The information that is obtained from the Raman spectroscopy is useful in analyzing various aspects of the material compositions. The Raman shifts and relative intensities of all Raman bands of the material allow identifying the material. The individual band changes and shifts which are seen as narrow, or broad can be varied with the intensity of the light. These changes can reveal information about the stresses in the sample and variation in crystallinity. The amount of material and its composition can also be identified, the variations in spectra with the position of the samples also reveal the changes in the material’s homogeneity. Advantages and disadvantages The advantages of Raman spectroscopy include its strength in specifying the chemicals in the materials which is a chemical fingerprint technique. There is no need for sample preparation and it is a non-destructive technique. The Raman spectra are acquired within a few seconds decreasing the processing time. The disadvantages of Raman spectroscopy include that it can not be used in analyzing metals and alloys, and in most cases, it is not quantitative regarding the composition. The Raman effect is weak and the detection needs a very sensitive and highly optimized instrument. The fluorescence of impurities or of the sample itself can hide the Raman spectrum. Reference [1] http://www.snlabs.com/raman-spectroscopy.html [2] Downes, A. and Elfick, A., 2010. Raman spectroscopy and related techniques in biomedicine. Sensors, 10(3), pp.1871-1889. [3] https://www.edinst.com/blog/what-is-raman-spectroscopy/ [4] https://www.sas.upenn.edu/~crulli/TheRamanSpectrophotometer.html

Fig-4 Schematic representation of Raman spectrometer with its components [4] Information from Raman spectroscopy The information that is obtained from the Raman spectroscopy is useful in analyzing various aspects of the material compositions. The Raman shifts and relative intensities of all Raman bands of the material allow identifying the material. The individual band changes and shifts which are seen as narrow, or broad can be varied with the intensity of the light. These changes can reveal information about the stresses in the sample and variation in crystallinity. The amount of material and its composition can also be identified, the variations in spectra with the position of the samples also reveal the changes in the material’s homogeneity. Advantages and disadvantages The advantages of Raman spectroscopy include its strength in specifying the chemicals in the materials which is a chemical fingerprint technique. There is no need for sample preparation and it is a non-destructive technique. The Raman spectra are acquired within a few seconds decreasing the processing time. The disadvantages of Raman spectroscopy include that it can not be used in analyzing metals and alloys, and in most cases, it is not quantitative regarding the composition. The Raman effect is weak and the detection needs a very sensitive and highly optimized instrument. The fluorescence of impurities or of the sample itself can hide the Raman spectrum. Reference [1] http://www.snlabs.com/raman-spectroscopy.html [2] Downes, A. and Elfick, A., 2010. Raman spectroscopy and related techniques in biomedicine. Sensors, 10(3), pp.1871-1889. [3] https://www.edinst.com/blog/what-is-raman-spectroscopy/ [4] https://www.sas.upenn.edu/~crulli/TheRamanSpectrophotometer.html

What is raman spectraused for

[3] https://www.edinst.com/blog/what-is-raman-spectroscopy/ [4] https://www.sas.upenn.edu/~crulli/TheRamanSpectrophotometer.html

Ramaneffect

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[1] http://www.snlabs.com/raman-spectroscopy.html [2] Downes, A. and Elfick, A., 2010. Raman spectroscopy and related techniques in biomedicine. Sensors, 10(3), pp.1871-1889. [3] https://www.edinst.com/blog/what-is-raman-spectroscopy/ [4] https://www.sas.upenn.edu/~crulli/TheRamanSpectrophotometer.html

Reference [1] http://www.snlabs.com/raman-spectroscopy.html [2] Downes, A. and Elfick, A., 2010. Raman spectroscopy and related techniques in biomedicine. Sensors, 10(3), pp.1871-1889. [3] https://www.edinst.com/blog/what-is-raman-spectroscopy/ [4] https://www.sas.upenn.edu/~crulli/TheRamanSpectrophotometer.html

The advantages of Raman spectroscopy include its strength in specifying the chemicals in the materials which is a chemical fingerprint technique. There is no need for sample preparation and it is a non-destructive technique. The Raman spectra are acquired within a few seconds decreasing the processing time. The disadvantages of Raman spectroscopy include that it can not be used in analyzing metals and alloys, and in most cases, it is not quantitative regarding the composition. The Raman effect is weak and the detection needs a very sensitive and highly optimized instrument. The fluorescence of impurities or of the sample itself can hide the Raman spectrum. Reference [1] http://www.snlabs.com/raman-spectroscopy.html [2] Downes, A. and Elfick, A., 2010. Raman spectroscopy and related techniques in biomedicine. Sensors, 10(3), pp.1871-1889. [3] https://www.edinst.com/blog/what-is-raman-spectroscopy/ [4] https://www.sas.upenn.edu/~crulli/TheRamanSpectrophotometer.html

Ramanspectroscopy instrumentation

Sometimes a carrier signal can carry more than one modulating information stream. Multiplexing combines the streams onto a single carrier -- e.g., by encoding a fixed-duration segment of one, then of the next, for example, cycling through all the channels before returning to the first -- a process called time-division multiplexing (TDM). Another form is frequency-division multiplexing (FDM), where multiple carriers of different frequencies are used on the same medium.

Radio and television broadcasts and satellite radio typically use AM or FM. Most short-range two-way radios -- up to tens of miles -- use FM, while longer-range two-way radios -- up to hundreds or thousands of miles -- typically employ a mode known as single sideband (SSB).

A device that performs both modulation and demodulation is called a modem -- a name created by combining the first letters of MOdulator and DEModulator.

Ramanpeak identification Table

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Fig-3 Raman scattering and Rayleigh scattering [3] Components of Raman spectrometer Laser source: The laser source is used for the excitation of the sample and resulting scattered light. Injection/rejection filter: The filter delivers the laser to the sample and allows the scattered Raman light to pass through to the spectrograph. Spectrograph: The spectrograph is used to divide the light into separated wavelengths and measure the light intensity at each wavelength. Microscope: The microscope is used to focus the laser light onto a point on the sample surface and collects the Raman light. Computer: It provides instrumental control and data handling and manipulation. Fig-4 Schematic representation of Raman spectrometer with its components [4] Information from Raman spectroscopy The information that is obtained from the Raman spectroscopy is useful in analyzing various aspects of the material compositions. The Raman shifts and relative intensities of all Raman bands of the material allow identifying the material. The individual band changes and shifts which are seen as narrow, or broad can be varied with the intensity of the light. These changes can reveal information about the stresses in the sample and variation in crystallinity. The amount of material and its composition can also be identified, the variations in spectra with the position of the samples also reveal the changes in the material’s homogeneity. Advantages and disadvantages The advantages of Raman spectroscopy include its strength in specifying the chemicals in the materials which is a chemical fingerprint technique. There is no need for sample preparation and it is a non-destructive technique. The Raman spectra are acquired within a few seconds decreasing the processing time. The disadvantages of Raman spectroscopy include that it can not be used in analyzing metals and alloys, and in most cases, it is not quantitative regarding the composition. The Raman effect is weak and the detection needs a very sensitive and highly optimized instrument. The fluorescence of impurities or of the sample itself can hide the Raman spectrum. Reference [1] http://www.snlabs.com/raman-spectroscopy.html [2] Downes, A. and Elfick, A., 2010. Raman spectroscopy and related techniques in biomedicine. Sensors, 10(3), pp.1871-1889. [3] https://www.edinst.com/blog/what-is-raman-spectroscopy/ [4] https://www.sas.upenn.edu/~crulli/TheRamanSpectrophotometer.html

The interaction of light on materials is very different it may be transmitted, reflected, or scattered; the wavelength of the light affects the interaction with materials in different colors. This study of light is called spectroscopy. Based on this an Indian physicist C.V Raman observed the scattering phenomenon where the light is scattered by the molecules and hence this phenomenon was named Raman scattering. The analysis/characterization technique that deals with Raman scattering is Raman spectroscopy. In Fig-1 Raman spectrometer from S & N lab is shown. Fig-1 Raman spectrometer from S & N lab [1] Definition Raman spectroscopy is the analytical technique where scattered light is used to measure the vibrational energy modes of the sample. This technique provides both the information on chemical and structural characteristics of the material and also the identification of substances. The Raman spectroscopy extracts the information through the detection of Raman scattering from the sample. Fig-2 is the schematic representation of the Raman spectrometer. Fig-2 Schematic representation of Raman spectrometer [2] Working principle The working principle of Raman spectroscopy is based on the inelastic scattering of monochromatic light from a laser source which changes its frequency upon interaction with the material. Photons from the laser are absorbed by the samples and it is remitted with a frequency shift up or down in comparison to the original monochromatic frequency this is called the Raman effect. These shifts in the frequency provide information about the rotational, vibrational, and other low-frequency transitions in the molecules. This technique can be used in studying the materials like solid, liquid, and gaseous nature. In order to understand spectroscopy better, we should know the difference between Rayleigh scattering and Raman scattering. Rayleigh scattering: In this case, the energy of the molecules is unchanged after the interaction with the molecules. The energy and the wavelength of the scattered photons are equal to that of the incident photon. Hence the energy of the scattering particle is conserved this is called Rayleigh scattering. Raman scattering: In this case, the light is scattered by the molecule, and the oscillating electromagnetic field of a photon induces a polarisation of the molecular electron cloud causing the molecules to be in a higher energy state with the energy of a photon is transferred to the molecule. This can be considered as the formation of a very short-lived complex between the photons and molecules which is commonly called the virtual state of molecules. The virtual state is not stable, and the photon is remitted almost immediately as scattered light. The schematic representation of the Raman and Rayleigh scattering is shown in Fig-3. Fig-3 Raman scattering and Rayleigh scattering [3] Components of Raman spectrometer Laser source: The laser source is used for the excitation of the sample and resulting scattered light. Injection/rejection filter: The filter delivers the laser to the sample and allows the scattered Raman light to pass through to the spectrograph. Spectrograph: The spectrograph is used to divide the light into separated wavelengths and measure the light intensity at each wavelength. Microscope: The microscope is used to focus the laser light onto a point on the sample surface and collects the Raman light. Computer: It provides instrumental control and data handling and manipulation. Fig-4 Schematic representation of Raman spectrometer with its components [4] Information from Raman spectroscopy The information that is obtained from the Raman spectroscopy is useful in analyzing various aspects of the material compositions. The Raman shifts and relative intensities of all Raman bands of the material allow identifying the material. The individual band changes and shifts which are seen as narrow, or broad can be varied with the intensity of the light. These changes can reveal information about the stresses in the sample and variation in crystallinity. The amount of material and its composition can also be identified, the variations in spectra with the position of the samples also reveal the changes in the material’s homogeneity. Advantages and disadvantages The advantages of Raman spectroscopy include its strength in specifying the chemicals in the materials which is a chemical fingerprint technique. There is no need for sample preparation and it is a non-destructive technique. The Raman spectra are acquired within a few seconds decreasing the processing time. The disadvantages of Raman spectroscopy include that it can not be used in analyzing metals and alloys, and in most cases, it is not quantitative regarding the composition. The Raman effect is weak and the detection needs a very sensitive and highly optimized instrument. The fluorescence of impurities or of the sample itself can hide the Raman spectrum. Reference [1] http://www.snlabs.com/raman-spectroscopy.html [2] Downes, A. and Elfick, A., 2010. Raman spectroscopy and related techniques in biomedicine. Sensors, 10(3), pp.1871-1889. [3] https://www.edinst.com/blog/what-is-raman-spectroscopy/ [4] https://www.sas.upenn.edu/~crulli/TheRamanSpectrophotometer.html

Fig-2 Schematic representation of Raman spectrometer [2] Working principle The working principle of Raman spectroscopy is based on the inelastic scattering of monochromatic light from a laser source which changes its frequency upon interaction with the material. Photons from the laser are absorbed by the samples and it is remitted with a frequency shift up or down in comparison to the original monochromatic frequency this is called the Raman effect. These shifts in the frequency provide information about the rotational, vibrational, and other low-frequency transitions in the molecules. This technique can be used in studying the materials like solid, liquid, and gaseous nature. In order to understand spectroscopy better, we should know the difference between Rayleigh scattering and Raman scattering. Rayleigh scattering: In this case, the energy of the molecules is unchanged after the interaction with the molecules. The energy and the wavelength of the scattered photons are equal to that of the incident photon. Hence the energy of the scattering particle is conserved this is called Rayleigh scattering. Raman scattering: In this case, the light is scattered by the molecule, and the oscillating electromagnetic field of a photon induces a polarisation of the molecular electron cloud causing the molecules to be in a higher energy state with the energy of a photon is transferred to the molecule. This can be considered as the formation of a very short-lived complex between the photons and molecules which is commonly called the virtual state of molecules. The virtual state is not stable, and the photon is remitted almost immediately as scattered light. The schematic representation of the Raman and Rayleigh scattering is shown in Fig-3. Fig-3 Raman scattering and Rayleigh scattering [3] Components of Raman spectrometer Laser source: The laser source is used for the excitation of the sample and resulting scattered light. Injection/rejection filter: The filter delivers the laser to the sample and allows the scattered Raman light to pass through to the spectrograph. Spectrograph: The spectrograph is used to divide the light into separated wavelengths and measure the light intensity at each wavelength. Microscope: The microscope is used to focus the laser light onto a point on the sample surface and collects the Raman light. Computer: It provides instrumental control and data handling and manipulation. Fig-4 Schematic representation of Raman spectrometer with its components [4] Information from Raman spectroscopy The information that is obtained from the Raman spectroscopy is useful in analyzing various aspects of the material compositions. The Raman shifts and relative intensities of all Raman bands of the material allow identifying the material. The individual band changes and shifts which are seen as narrow, or broad can be varied with the intensity of the light. These changes can reveal information about the stresses in the sample and variation in crystallinity. The amount of material and its composition can also be identified, the variations in spectra with the position of the samples also reveal the changes in the material’s homogeneity. Advantages and disadvantages The advantages of Raman spectroscopy include its strength in specifying the chemicals in the materials which is a chemical fingerprint technique. There is no need for sample preparation and it is a non-destructive technique. The Raman spectra are acquired within a few seconds decreasing the processing time. The disadvantages of Raman spectroscopy include that it can not be used in analyzing metals and alloys, and in most cases, it is not quantitative regarding the composition. The Raman effect is weak and the detection needs a very sensitive and highly optimized instrument. The fluorescence of impurities or of the sample itself can hide the Raman spectrum. Reference [1] http://www.snlabs.com/raman-spectroscopy.html [2] Downes, A. and Elfick, A., 2010. Raman spectroscopy and related techniques in biomedicine. Sensors, 10(3), pp.1871-1889. [3] https://www.edinst.com/blog/what-is-raman-spectroscopy/ [4] https://www.sas.upenn.edu/~crulli/TheRamanSpectrophotometer.html

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Modulation schemes can be analog or digital. An analog scheme has an input wave that varies continuously like a sine wave. In digital modulation scheme, voice is sampled at some rate and then compressed and turned into a bit stream, and this in turn is created into a particular kind of wave which is then superimposed on the carrier signal.

Fig-1 Raman spectrometer from S & N lab [1] Definition Raman spectroscopy is the analytical technique where scattered light is used to measure the vibrational energy modes of the sample. This technique provides both the information on chemical and structural characteristics of the material and also the identification of substances. The Raman spectroscopy extracts the information through the detection of Raman scattering from the sample. Fig-2 is the schematic representation of the Raman spectrometer. Fig-2 Schematic representation of Raman spectrometer [2] Working principle The working principle of Raman spectroscopy is based on the inelastic scattering of monochromatic light from a laser source which changes its frequency upon interaction with the material. Photons from the laser are absorbed by the samples and it is remitted with a frequency shift up or down in comparison to the original monochromatic frequency this is called the Raman effect. These shifts in the frequency provide information about the rotational, vibrational, and other low-frequency transitions in the molecules. This technique can be used in studying the materials like solid, liquid, and gaseous nature. In order to understand spectroscopy better, we should know the difference between Rayleigh scattering and Raman scattering. Rayleigh scattering: In this case, the energy of the molecules is unchanged after the interaction with the molecules. The energy and the wavelength of the scattered photons are equal to that of the incident photon. Hence the energy of the scattering particle is conserved this is called Rayleigh scattering. Raman scattering: In this case, the light is scattered by the molecule, and the oscillating electromagnetic field of a photon induces a polarisation of the molecular electron cloud causing the molecules to be in a higher energy state with the energy of a photon is transferred to the molecule. This can be considered as the formation of a very short-lived complex between the photons and molecules which is commonly called the virtual state of molecules. The virtual state is not stable, and the photon is remitted almost immediately as scattered light. The schematic representation of the Raman and Rayleigh scattering is shown in Fig-3. Fig-3 Raman scattering and Rayleigh scattering [3] Components of Raman spectrometer Laser source: The laser source is used for the excitation of the sample and resulting scattered light. Injection/rejection filter: The filter delivers the laser to the sample and allows the scattered Raman light to pass through to the spectrograph. Spectrograph: The spectrograph is used to divide the light into separated wavelengths and measure the light intensity at each wavelength. Microscope: The microscope is used to focus the laser light onto a point on the sample surface and collects the Raman light. Computer: It provides instrumental control and data handling and manipulation. Fig-4 Schematic representation of Raman spectrometer with its components [4] Information from Raman spectroscopy The information that is obtained from the Raman spectroscopy is useful in analyzing various aspects of the material compositions. The Raman shifts and relative intensities of all Raman bands of the material allow identifying the material. The individual band changes and shifts which are seen as narrow, or broad can be varied with the intensity of the light. These changes can reveal information about the stresses in the sample and variation in crystallinity. The amount of material and its composition can also be identified, the variations in spectra with the position of the samples also reveal the changes in the material’s homogeneity. Advantages and disadvantages The advantages of Raman spectroscopy include its strength in specifying the chemicals in the materials which is a chemical fingerprint technique. There is no need for sample preparation and it is a non-destructive technique. The Raman spectra are acquired within a few seconds decreasing the processing time. The disadvantages of Raman spectroscopy include that it can not be used in analyzing metals and alloys, and in most cases, it is not quantitative regarding the composition. The Raman effect is weak and the detection needs a very sensitive and highly optimized instrument. The fluorescence of impurities or of the sample itself can hide the Raman spectrum. Reference [1] http://www.snlabs.com/raman-spectroscopy.html [2] Downes, A. and Elfick, A., 2010. Raman spectroscopy and related techniques in biomedicine. Sensors, 10(3), pp.1871-1889. [3] https://www.edinst.com/blog/what-is-raman-spectroscopy/ [4] https://www.sas.upenn.edu/~crulli/TheRamanSpectrophotometer.html

Modulation is usually applied to electromagnetic signals: radio waves, lasers/optics and computer networks. Modulation can even be applied to a direct current -- which can be treated as a degenerate carrier wave with a fixed amplitude and frequency of 0 Hz -- mainly by turning it on and off, as in Morse code telegraphy or a digital current loop interface. The special case of no carrier -- a response message indicating an attached device is no longer connected to a remote system -- is called baseband modulation.

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PSK conveys data by modulating the phase of the carrier signal by varying the sine and cosine inputs at precise times. PSK is used widely for wireless LANs, RFID and Bluetooth communications. The demodulator determines the phase of the signal received and translates it back to the symbol it represents.

A carrier signal is used to reduce the wavelength for efficient transmission and reception. Because the optimum antenna size is one-half or one-quarter of a wavelength, an audio frequency of 3000 Hz would need a wavelength of 100 km and a 25-kilometer antenna. Instead, using an FM carrier of 100 MHz, with a wavelength of 3 meters, the antenna would only need to be 80 cm long.

In another form, wavelength-division multiplexing (WDM) modulates multiple laser wavelengths/frequencies on long-haul fiber links to increase the total available bandwidth.

Ramanspectroscopy diagram

What is raman spectraand how does it work

Information can be added to the carrier by varying its amplitude, frequency, phase, polarization -- for optical signals -- and even quantum-level phenomena like spin.

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Modulation is the process of converting data into radio waves by adding information to an electronic or optical carrier signal. A carrier signal is one with a steady waveform -- constant height, or amplitude, and frequency.

The information that is obtained from the Raman spectroscopy is useful in analyzing various aspects of the material compositions. The Raman shifts and relative intensities of all Raman bands of the material allow identifying the material. The individual band changes and shifts which are seen as narrow, or broad can be varied with the intensity of the light. These changes can reveal information about the stresses in the sample and variation in crystallinity. The amount of material and its composition can also be identified, the variations in spectra with the position of the samples also reveal the changes in the material’s homogeneity. Advantages and disadvantages The advantages of Raman spectroscopy include its strength in specifying the chemicals in the materials which is a chemical fingerprint technique. There is no need for sample preparation and it is a non-destructive technique. The Raman spectra are acquired within a few seconds decreasing the processing time. The disadvantages of Raman spectroscopy include that it can not be used in analyzing metals and alloys, and in most cases, it is not quantitative regarding the composition. The Raman effect is weak and the detection needs a very sensitive and highly optimized instrument. The fluorescence of impurities or of the sample itself can hide the Raman spectrum. Reference [1] http://www.snlabs.com/raman-spectroscopy.html [2] Downes, A. and Elfick, A., 2010. Raman spectroscopy and related techniques in biomedicine. Sensors, 10(3), pp.1871-1889. [3] https://www.edinst.com/blog/what-is-raman-spectroscopy/ [4] https://www.sas.upenn.edu/~crulli/TheRamanSpectrophotometer.html

More complex forms of modulation include phase-shift keying (PSK) and QAM. Modern Wi-Fi modulation uses a combination of PSK and QAM64 or QAM256 to encode multiple bits of information into each transmitted symbol.

The disadvantages of Raman spectroscopy include that it can not be used in analyzing metals and alloys, and in most cases, it is not quantitative regarding the composition. The Raman effect is weak and the detection needs a very sensitive and highly optimized instrument. The fluorescence of impurities or of the sample itself can hide the Raman spectrum. Reference [1] http://www.snlabs.com/raman-spectroscopy.html [2] Downes, A. and Elfick, A., 2010. Raman spectroscopy and related techniques in biomedicine. Sensors, 10(3), pp.1871-1889. [3] https://www.edinst.com/blog/what-is-raman-spectroscopy/ [4] https://www.sas.upenn.edu/~crulli/TheRamanSpectrophotometer.html

Ramanspectroscopy PDF

In wireless communications, the duty cycle is the proportion of time that the wireless network transmits RF signals. The duty cycle is thus an important factor in assessing the electromagnetic radiation to which a person is exposed. The actual duty cycle can vary, depending on the data load on the network and the network speed. So, the duty cycle can be affected by whether the network is being used for VoIP, streaming videos or videos, etc.

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[2] Downes, A. and Elfick, A., 2010. Raman spectroscopy and related techniques in biomedicine. Sensors, 10(3), pp.1871-1889. [3] https://www.edinst.com/blog/what-is-raman-spectroscopy/ [4] https://www.sas.upenn.edu/~crulli/TheRamanSpectrophotometer.html

Multiple carriers of different frequencies can often be transmitted over a single media, with each carrier being modulated by an independent signal. For example, Wi-Fi uses individual channels to simultaneously transmit data to and from multiple clients.

What is raman spectrain chemistry

A computer audio modem allows a computer to connect to another computer or to a data network over a regular analog phone line by using the data signal to modulate an analog audio tone. A modem at the far end demodulates the audio signal to recover the data stream. A cable modem uses network data to modulate the cable service carrier signal.

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I am a postgraduate researcher at the University of Leeds. I have completed my master's degree in the Erasmus Tribos program at the University of Leeds, University of Ljubljana, and University of Coimbra and my bachelor's degree in Mechanical Engineering from VTU in NMIT, India. I am an editor and social networking manager at TriboNet. I have a YouTube channel called Tribo Geek where I upload videos on travel, research life, and topics for master's and PhD students.

Raman spectroscopy is the analytical technique where scattered light is used to measure the vibrational energy modes of the sample. This technique provides both the information on chemical and structural characteristics of the material and also the identification of substances. The Raman spectroscopy extracts the information through the detection of Raman scattering from the sample. Fig-2 is the schematic representation of the Raman spectrometer. Fig-2 Schematic representation of Raman spectrometer [2] Working principle The working principle of Raman spectroscopy is based on the inelastic scattering of monochromatic light from a laser source which changes its frequency upon interaction with the material. Photons from the laser are absorbed by the samples and it is remitted with a frequency shift up or down in comparison to the original monochromatic frequency this is called the Raman effect. These shifts in the frequency provide information about the rotational, vibrational, and other low-frequency transitions in the molecules. This technique can be used in studying the materials like solid, liquid, and gaseous nature. In order to understand spectroscopy better, we should know the difference between Rayleigh scattering and Raman scattering. Rayleigh scattering: In this case, the energy of the molecules is unchanged after the interaction with the molecules. The energy and the wavelength of the scattered photons are equal to that of the incident photon. Hence the energy of the scattering particle is conserved this is called Rayleigh scattering. Raman scattering: In this case, the light is scattered by the molecule, and the oscillating electromagnetic field of a photon induces a polarisation of the molecular electron cloud causing the molecules to be in a higher energy state with the energy of a photon is transferred to the molecule. This can be considered as the formation of a very short-lived complex between the photons and molecules which is commonly called the virtual state of molecules. The virtual state is not stable, and the photon is remitted almost immediately as scattered light. The schematic representation of the Raman and Rayleigh scattering is shown in Fig-3. Fig-3 Raman scattering and Rayleigh scattering [3] Components of Raman spectrometer Laser source: The laser source is used for the excitation of the sample and resulting scattered light. Injection/rejection filter: The filter delivers the laser to the sample and allows the scattered Raman light to pass through to the spectrograph. Spectrograph: The spectrograph is used to divide the light into separated wavelengths and measure the light intensity at each wavelength. Microscope: The microscope is used to focus the laser light onto a point on the sample surface and collects the Raman light. Computer: It provides instrumental control and data handling and manipulation. Fig-4 Schematic representation of Raman spectrometer with its components [4] Information from Raman spectroscopy The information that is obtained from the Raman spectroscopy is useful in analyzing various aspects of the material compositions. The Raman shifts and relative intensities of all Raman bands of the material allow identifying the material. The individual band changes and shifts which are seen as narrow, or broad can be varied with the intensity of the light. These changes can reveal information about the stresses in the sample and variation in crystallinity. The amount of material and its composition can also be identified, the variations in spectra with the position of the samples also reveal the changes in the material’s homogeneity. Advantages and disadvantages The advantages of Raman spectroscopy include its strength in specifying the chemicals in the materials which is a chemical fingerprint technique. There is no need for sample preparation and it is a non-destructive technique. The Raman spectra are acquired within a few seconds decreasing the processing time. The disadvantages of Raman spectroscopy include that it can not be used in analyzing metals and alloys, and in most cases, it is not quantitative regarding the composition. The Raman effect is weak and the detection needs a very sensitive and highly optimized instrument. The fluorescence of impurities or of the sample itself can hide the Raman spectrum. Reference [1] http://www.snlabs.com/raman-spectroscopy.html [2] Downes, A. and Elfick, A., 2010. Raman spectroscopy and related techniques in biomedicine. Sensors, 10(3), pp.1871-1889. [3] https://www.edinst.com/blog/what-is-raman-spectroscopy/ [4] https://www.sas.upenn.edu/~crulli/TheRamanSpectrophotometer.html

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