SPECTROSCOPY EXAM QUESTIONS AND ANSWERS
2025 #12
What is spectroscopy? - correct answer - General term for the science of the interaction
of radiation with
Matter
- The measurement of a sample's interaction with light of different wavelengths from
different
Regions of the electromagnetic spectrum.
How did spectroscopy originate and how to we use it today? - correct answer -
Historically, spectroscopy originated through the study of visible light dispersed
according to
Its wavelength, by a prism.
- Later the concept was expanded greatly to comprise any interaction with radiative
energy as
A function of its wavelength or frequency.
How is spectroscopic data presented? - correct answer As a spectrum - a plot of the
response of interest as a
Function of wavelength or frequency
What are the components of a typical spectrometer? Briefly explain each component. -
correct answer 1. Source of energy
• Provides an output that is both intense and stable
• Classified as either continuum or line sources
• Continuum source: emits radiation over a broad range of wavelengths (Example:
Deuterium lamp for UV-vis spectrophotometer - continuum source from 110 - 400 nm)
• Line sources: emits radiation at selected wavelengths (Example: laser for Raman
spectrometer - line source in visible (532 nm))
2. Means for isolating a narrow range of wavelengths.
3. Detector for measuring the signal.
4. Signal processor displaying the signal in a convenient form for the analyst.
What is the electromagnetic spectrum? - correct answer Covers many orders of
magnitude in frequency and wavelength.
If you double the frequency, you _______ the energy. - correct answer Double
If you double the wavelength, you _____ the energy. - correct answer Halve
What are the two ways in which light can be described? Define these in different ways. -
correct answer 1. Wave-like properties: terms such as wavelength and frequency ;
oscillating electric and magnetic fields
2. Particle-like properties: these are expressed in terms of packets of energy
Called photons
,What is a photon? - correct answer - A particle of electromagnetic radiation that has
zero mass and carries a
Quantum of energy.
- When a photon is absorbed by a sample, its energy is acquired by the sample.
What is a wavenumber? - correct answer - The reciprocal of the wavelength in
Centimeters, is another way of describing electromagnetic radiation.
Why is a wavenumber a useful characteristic? - correct answer Directly proportional to
the frequency, and thus the energy of radiation
Which of the ways that light can be described, is associated with the absorption and
emission of radian energy? - correct answer Treat electromagnetic
Radiation not as a collection of waves but rather as a stream of discrete particles
Called photons or quanta.
- The need for a particle model for radiation became apparent as a consequence of the
Photoelectric effect.
Describe the terms associated with wave characteristics - wavelength frequency,
period, and amplitude. - correct answer - Wavelength (λ) is the linear distance between
Any two equivalent points on successive
Waves (successive maxima or minima).
- Frequency (ʋ) is the number of oscillations of
The field that occur per second and is equal of
1/p.
- Period (p) is the time in seconds required for
The passage of successive maxima or minima
Through a fixed point in space.
- Amplitude (A) of the sinusoidal wave is the
Length of the electric vector at a maximum in
The wave.
What is defraction? - correct answer A parallel beam of radiation is bent as it passes by
a sharp barrier or through a narrow opening.
Which wave theory of light is used to best describe the electromagnetic spectrum? -
correct answer Particle Theory
What is absorption? - correct answer Electromagnetic radiation
From a source is absorbed by the
Sample and increases the energy of a molecule.
What is emission? - correct answer Electromagnetic radiation
Emanates from the sample and
Decreases the energy of the molecule.
, As spectroscopists, we know that we get information about a sample from its interaction
with radiation. What are we measuring and how is this information expressed? - correct
answer - Measuring the electromagnetic radiation emitted as it returns to the ground
state or by measuring the amount of EM radiation
Absorbed or scattered as a result of the excitation.
- The results of this measurement are often expressed graphically by a spectrum, which
is a
Plot of the emitted radiation as a function of frequency or wavelength.
What are the different outcomes of the interaction of radiation with matter? Explain
each. - correct answer - Reflected radiation: when light waves strike a surface and
bounce off and fly
Into space
• If the surface is smooth, the outgoing waves all move in the same direction.
• If the surface
- Scattering of EM radiation is caused by the
Interaction of radiation with matter resulting in the reradiation of part of the energy to
other directions not along the
Path of the incident radiation.
- Absorption of EM radiation promotes some
Of the analyte species to an excited state.
• In absorption spectroscopy, we measure the
Amount of light absorbed as a function of
Wavelength
What was the first spectroscopy technique developed? Briefly describe how this
technique works. - correct answer
The energy E associated with the bands of a molecule is made up of three components
what are they and briefly describe each? - correct answer E = Eelectronic + Evibrational
+ Erotational
- Eelectronic describes the electronic energy of the molecule that arises from the energy
states of its
Several bonding electrons
- Evibrational refers to the total energy associated with the multitude of interatomic
vibrations that
Are present in molecular species.
- Erotational is the energy caused by various rotational motions within a molecule
What are the three types of relaxation processes that permit an atom or molecule to
return to its ground state? Briefly describe. - correct answer 1. Nonradiative relaxation
• Involves the loss of energy in a series of small steps, the excitation energy being
converted to
Kinetic energy by collision with other molecules.
2025 #12
What is spectroscopy? - correct answer - General term for the science of the interaction
of radiation with
Matter
- The measurement of a sample's interaction with light of different wavelengths from
different
Regions of the electromagnetic spectrum.
How did spectroscopy originate and how to we use it today? - correct answer -
Historically, spectroscopy originated through the study of visible light dispersed
according to
Its wavelength, by a prism.
- Later the concept was expanded greatly to comprise any interaction with radiative
energy as
A function of its wavelength or frequency.
How is spectroscopic data presented? - correct answer As a spectrum - a plot of the
response of interest as a
Function of wavelength or frequency
What are the components of a typical spectrometer? Briefly explain each component. -
correct answer 1. Source of energy
• Provides an output that is both intense and stable
• Classified as either continuum or line sources
• Continuum source: emits radiation over a broad range of wavelengths (Example:
Deuterium lamp for UV-vis spectrophotometer - continuum source from 110 - 400 nm)
• Line sources: emits radiation at selected wavelengths (Example: laser for Raman
spectrometer - line source in visible (532 nm))
2. Means for isolating a narrow range of wavelengths.
3. Detector for measuring the signal.
4. Signal processor displaying the signal in a convenient form for the analyst.
What is the electromagnetic spectrum? - correct answer Covers many orders of
magnitude in frequency and wavelength.
If you double the frequency, you _______ the energy. - correct answer Double
If you double the wavelength, you _____ the energy. - correct answer Halve
What are the two ways in which light can be described? Define these in different ways. -
correct answer 1. Wave-like properties: terms such as wavelength and frequency ;
oscillating electric and magnetic fields
2. Particle-like properties: these are expressed in terms of packets of energy
Called photons
,What is a photon? - correct answer - A particle of electromagnetic radiation that has
zero mass and carries a
Quantum of energy.
- When a photon is absorbed by a sample, its energy is acquired by the sample.
What is a wavenumber? - correct answer - The reciprocal of the wavelength in
Centimeters, is another way of describing electromagnetic radiation.
Why is a wavenumber a useful characteristic? - correct answer Directly proportional to
the frequency, and thus the energy of radiation
Which of the ways that light can be described, is associated with the absorption and
emission of radian energy? - correct answer Treat electromagnetic
Radiation not as a collection of waves but rather as a stream of discrete particles
Called photons or quanta.
- The need for a particle model for radiation became apparent as a consequence of the
Photoelectric effect.
Describe the terms associated with wave characteristics - wavelength frequency,
period, and amplitude. - correct answer - Wavelength (λ) is the linear distance between
Any two equivalent points on successive
Waves (successive maxima or minima).
- Frequency (ʋ) is the number of oscillations of
The field that occur per second and is equal of
1/p.
- Period (p) is the time in seconds required for
The passage of successive maxima or minima
Through a fixed point in space.
- Amplitude (A) of the sinusoidal wave is the
Length of the electric vector at a maximum in
The wave.
What is defraction? - correct answer A parallel beam of radiation is bent as it passes by
a sharp barrier or through a narrow opening.
Which wave theory of light is used to best describe the electromagnetic spectrum? -
correct answer Particle Theory
What is absorption? - correct answer Electromagnetic radiation
From a source is absorbed by the
Sample and increases the energy of a molecule.
What is emission? - correct answer Electromagnetic radiation
Emanates from the sample and
Decreases the energy of the molecule.
, As spectroscopists, we know that we get information about a sample from its interaction
with radiation. What are we measuring and how is this information expressed? - correct
answer - Measuring the electromagnetic radiation emitted as it returns to the ground
state or by measuring the amount of EM radiation
Absorbed or scattered as a result of the excitation.
- The results of this measurement are often expressed graphically by a spectrum, which
is a
Plot of the emitted radiation as a function of frequency or wavelength.
What are the different outcomes of the interaction of radiation with matter? Explain
each. - correct answer - Reflected radiation: when light waves strike a surface and
bounce off and fly
Into space
• If the surface is smooth, the outgoing waves all move in the same direction.
• If the surface
- Scattering of EM radiation is caused by the
Interaction of radiation with matter resulting in the reradiation of part of the energy to
other directions not along the
Path of the incident radiation.
- Absorption of EM radiation promotes some
Of the analyte species to an excited state.
• In absorption spectroscopy, we measure the
Amount of light absorbed as a function of
Wavelength
What was the first spectroscopy technique developed? Briefly describe how this
technique works. - correct answer
The energy E associated with the bands of a molecule is made up of three components
what are they and briefly describe each? - correct answer E = Eelectronic + Evibrational
+ Erotational
- Eelectronic describes the electronic energy of the molecule that arises from the energy
states of its
Several bonding electrons
- Evibrational refers to the total energy associated with the multitude of interatomic
vibrations that
Are present in molecular species.
- Erotational is the energy caused by various rotational motions within a molecule
What are the three types of relaxation processes that permit an atom or molecule to
return to its ground state? Briefly describe. - correct answer 1. Nonradiative relaxation
• Involves the loss of energy in a series of small steps, the excitation energy being
converted to
Kinetic energy by collision with other molecules.
