MMSC 407 Exam 1 (A+ Graded)
wavelegnth correct answers the distance between the crests (peaks) of 2 successive waves
amplitude correct answers the height of a wave
frequency correct answers the number of waves which pass by a stationary point in one second
-is related to speed
lower (fill in the blank) correct answers longer wavelegnths are associated with being (higher /
lower) in energy
visible spectrum correct answers the portion of the electromagentic spectrum which produces
wavelegnths that can be seen by the naked eye
-red: longest wavelegnth, lowest energy
-violet: shortest wavelength, highest energy
electromagnetic spectrum correct answers HIGHEST ENERGY (short wavelength)
-cosmic
-gamma rays
-X rays
-ultraviolet
-visible (Violet, blue, green, yellow, orange, red)
-infrared
-microwaves
LOWEST ENERGY (long wavelegnth
short (fill in the blank) correct answers high frequency= high energy = ____________
wavelengths
long (fill in the blank) correct answers low frequency= low energy= _____________ size
wavelengths
reflected light correct answers light that encounters a solution and is forced to bounce back in the
direction it came from
-does not travel through the solution
absorbed light correct answers light that enters a solution, and is absorbed by the material
-the light comes into the solution does NOT pass through the solution
transmitted light correct answers light that enters the solution is able to pass through the solution
-light comes into the solution and passes through
diffracted light correct answers light that enters a solution and changes direction
-light bounces out of the solution at an angle
,fluoresced light correct answers light that enters a solutions and becomes absorbed, and then
emitted at a different (usually longer and visible) wavelegnth
transparent correct answers all light is able to pass through
-a clear substance that allows all light through
translucent correct answers some light is able to pass through
-a cloudy substance that does not let all light through
opaque correct answers no light passes through
-a VERY hazy solution that lets no light through
diffraction correct answers white light is sent through a slit (diffraction grating) and the slit
causes bending of light (change in direction of light beam), which reveals all visible wavelengths
of light to be seen
-long wavelengths (low energy, like red) bend the least
-short wavelengths (high energy, like blue) bend the most
percent transmittance (%T) correct answers Bouguer's Law
- light transmitted / original light
-when more light is absorbed, there is naturally less light that is being transmitted
inverse (fill in the blank) correct answers light transmittance (T) and absorbance have a
___________ logarithmic relationship
-the more light that is absorbed, the less light there is left to be transmitted
absorbance assumptions correct answers to read absorbance 2 factors are assumed
-monochromatic light: it is assumed that only a single wavelength of light is being used
-logarithmic relationship: as absorbance increases the %T (% transmission of light) goes down
logarithmically
absorbance correct answers a value that is CALCULATED (not measured) based on %T to
determine how much of the light is absorbed
-%T is measured and then that value is used with a logarithmic equation to calculate A
-calculated using Beer Lambert law
-has no units (units cancel each other out in the equation)
lambert's law correct answers law that states that absorbance increases as the thickness of the
absorbing material increases
-when the same solution is put in a thick cuvette and a thin cuvette and a thick cuvette, the thick
cuvette will have a higher absorbance
Beer's law correct answers A=abc
-absorbance (A) is directly proportional to the concentration (c) of the absorbing substance in a
solution
-A= absorbance
, -a= molar absorptivity
-b= light path through the solution
-c= concentration of substance
-all of the units that are multiplied together cancel each other out, so there is no units for A
molar absorptivity correct answers a in Beer's law
-constant for a given compound at certain conditions (temperature, pH, etc.)
-remains constant because you use the same conditions the whole time
-L/mol*cm
light path of the solution correct answers b in Beer's law
-path of light through the cuvette (equal to the width of the cuvette)
-remains constant because you use the same cuvette the whole time
-cm
concentration of substance correct answers c in Beer's law
-the only factor that is changing (because a and b are supposed to be constant), therefore is the
factor that is responsible for changes in A
-mol/L
calculating absorbance correct answers **absorbance cannot be directly measured**
-instrument is used to read %T
-instrument converts %T into absorbance
-instrument compares the sample absorbance with the known absorbance of a standard (a known
value at a certain wavelegnth), and uses this to calculate the concentration of analyte (using
Beer's law)
spectrophotometry correct answers measurement of intensity of light at selected wavelegnths to
quantify the concentration of analytes
-concentrations are determined based on the amount of light that is absorbed in the solution,
compared to the standard (solvent containing no solute)
-the machine actually measures the %T, and uses this to calculate absorbance
-the more concentrated a solution is, the higher the absorbance will be (more light is absorbed by
more particles in the solution)
-more more concentrated a solution is, the lower the %T is (more particles in the solution means
less light is able to pass through)
spectrophotometer correct answers -light source: supplies light wavelegnth
-entrance slit: ensures no excess light enters the system
-monochromator: separates the light source into the individual desired wavelength
-sample container (cuvette): holds the sample that the light is intended to pass through
-detector system (photodetector): measures the % transmittance of light through the sample
-readout device: converts the measured % transmittance to an absorbance value
light source correct answers produces light in spectrophotometer, will be chosen based on what
wavelength is needed
wavelegnth correct answers the distance between the crests (peaks) of 2 successive waves
amplitude correct answers the height of a wave
frequency correct answers the number of waves which pass by a stationary point in one second
-is related to speed
lower (fill in the blank) correct answers longer wavelegnths are associated with being (higher /
lower) in energy
visible spectrum correct answers the portion of the electromagentic spectrum which produces
wavelegnths that can be seen by the naked eye
-red: longest wavelegnth, lowest energy
-violet: shortest wavelength, highest energy
electromagnetic spectrum correct answers HIGHEST ENERGY (short wavelength)
-cosmic
-gamma rays
-X rays
-ultraviolet
-visible (Violet, blue, green, yellow, orange, red)
-infrared
-microwaves
LOWEST ENERGY (long wavelegnth
short (fill in the blank) correct answers high frequency= high energy = ____________
wavelengths
long (fill in the blank) correct answers low frequency= low energy= _____________ size
wavelengths
reflected light correct answers light that encounters a solution and is forced to bounce back in the
direction it came from
-does not travel through the solution
absorbed light correct answers light that enters a solution, and is absorbed by the material
-the light comes into the solution does NOT pass through the solution
transmitted light correct answers light that enters the solution is able to pass through the solution
-light comes into the solution and passes through
diffracted light correct answers light that enters a solution and changes direction
-light bounces out of the solution at an angle
,fluoresced light correct answers light that enters a solutions and becomes absorbed, and then
emitted at a different (usually longer and visible) wavelegnth
transparent correct answers all light is able to pass through
-a clear substance that allows all light through
translucent correct answers some light is able to pass through
-a cloudy substance that does not let all light through
opaque correct answers no light passes through
-a VERY hazy solution that lets no light through
diffraction correct answers white light is sent through a slit (diffraction grating) and the slit
causes bending of light (change in direction of light beam), which reveals all visible wavelengths
of light to be seen
-long wavelengths (low energy, like red) bend the least
-short wavelengths (high energy, like blue) bend the most
percent transmittance (%T) correct answers Bouguer's Law
- light transmitted / original light
-when more light is absorbed, there is naturally less light that is being transmitted
inverse (fill in the blank) correct answers light transmittance (T) and absorbance have a
___________ logarithmic relationship
-the more light that is absorbed, the less light there is left to be transmitted
absorbance assumptions correct answers to read absorbance 2 factors are assumed
-monochromatic light: it is assumed that only a single wavelength of light is being used
-logarithmic relationship: as absorbance increases the %T (% transmission of light) goes down
logarithmically
absorbance correct answers a value that is CALCULATED (not measured) based on %T to
determine how much of the light is absorbed
-%T is measured and then that value is used with a logarithmic equation to calculate A
-calculated using Beer Lambert law
-has no units (units cancel each other out in the equation)
lambert's law correct answers law that states that absorbance increases as the thickness of the
absorbing material increases
-when the same solution is put in a thick cuvette and a thin cuvette and a thick cuvette, the thick
cuvette will have a higher absorbance
Beer's law correct answers A=abc
-absorbance (A) is directly proportional to the concentration (c) of the absorbing substance in a
solution
-A= absorbance
, -a= molar absorptivity
-b= light path through the solution
-c= concentration of substance
-all of the units that are multiplied together cancel each other out, so there is no units for A
molar absorptivity correct answers a in Beer's law
-constant for a given compound at certain conditions (temperature, pH, etc.)
-remains constant because you use the same conditions the whole time
-L/mol*cm
light path of the solution correct answers b in Beer's law
-path of light through the cuvette (equal to the width of the cuvette)
-remains constant because you use the same cuvette the whole time
-cm
concentration of substance correct answers c in Beer's law
-the only factor that is changing (because a and b are supposed to be constant), therefore is the
factor that is responsible for changes in A
-mol/L
calculating absorbance correct answers **absorbance cannot be directly measured**
-instrument is used to read %T
-instrument converts %T into absorbance
-instrument compares the sample absorbance with the known absorbance of a standard (a known
value at a certain wavelegnth), and uses this to calculate the concentration of analyte (using
Beer's law)
spectrophotometry correct answers measurement of intensity of light at selected wavelegnths to
quantify the concentration of analytes
-concentrations are determined based on the amount of light that is absorbed in the solution,
compared to the standard (solvent containing no solute)
-the machine actually measures the %T, and uses this to calculate absorbance
-the more concentrated a solution is, the higher the absorbance will be (more light is absorbed by
more particles in the solution)
-more more concentrated a solution is, the lower the %T is (more particles in the solution means
less light is able to pass through)
spectrophotometer correct answers -light source: supplies light wavelegnth
-entrance slit: ensures no excess light enters the system
-monochromator: separates the light source into the individual desired wavelength
-sample container (cuvette): holds the sample that the light is intended to pass through
-detector system (photodetector): measures the % transmittance of light through the sample
-readout device: converts the measured % transmittance to an absorbance value
light source correct answers produces light in spectrophotometer, will be chosen based on what
wavelength is needed
