CC HARR Exam Questions with Save
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Terms in this set (530)
Which formula correctly D
describes the relationship
between absorbance and
%T?
A. A = 2 - log %T
B. A = log 1/T
C. A = -log T
D. all of these options
A solution that has a 2.0
transmittance of 1.0 %T
would have an
absorbance of:
absorbance is directly proportional to
concentration
Beer's law states that A = a × b × c, where a is the
absorptivity coefficient (a constant), b is the path
In absorption
length, and c is concentration. Absorbance is
spectrophotometry:
directly proportional to both b and c. Doubling the
path length results in incident light contacting twice
the number of molecules in solution. This causes
absorbance to double, the same effect as doubling
the concentration of molecules.
,Which wavelength would 450 nm
be absorbed strongly by
a red-colored solution? A solution transmits light corresponding in
A. 450 nm wavelength to its color, and usually absorbs light of
B. 585 nm wavelengths complementary to its color. A red
C. 600 nm solution transmits light of 600-650 nm and strongly
D. 650 nm absorbs 400-500 nm light.
525 nm
A green-colored solution
would show highest Green light consists of wavelengths from 500-550
transmittance at: nm. A green-colored solution with a transmittance
A. 475 nm maximum of 525 nm and a 50-nm bandpass
B. 525 nm transmits light of 525 nm and absorbs light below
C. 585 nm 475 nm and above 575 nm. A solution that is green
D. 620 nm would be quantitated using a wavelength that it
absorbs strongly, such as 450 nm.
,SITUATION: A Replace the source lamp
technologist is
performing an enzyme Visible spectrophotometers are usually supplied
assay at 340 nm using a with a tungsten or quartz halogen source lamp.
visible-range Tungsten lamps produce a continuous range of
spectrophotometer. After wavelengths from about 320-2,000 nm. Output
setting the wavelength increases as wavelength becomes longer peaking at
and adjusting the readout around 1,000 nm, and is poor below 400 nm. As the
to zero %T with the light lamp envelope darkens with age, the amount of
path blocked, a cuvette light reaching the photodetector at 340 nm
with deionized water is becomes insufficient to set the blank reading to
inserted. With the light 100%T. Quartz halogen lamps produce light from
path fully open and the 300 nm through the infrared region. Deuterium or
100%T control at hydrogen lamps produce ultraviolet-rich spectra
maximum, the instrument optimal for ultraviolet (UV) work. Mercury vapor
readout will not rise lamps produce a discontinuous spectrum that
above 90%T. What is the includes a high output at around 365 nm that is
most appropriate first useful for fluorescent applications. Xenon lamps
course of action? generate a continuous spectrum of fairly uniform
A. Replace the source intensity from 300-2,000 nm, making them useful for
lamp both visible and UV applications.
B. Insert a wider cuvette
into the light path
C. Measure the voltage
across the lamp terminals
D. Replace the instrument
fuse
A prism and a variable exit slit
Diffraction gratings and prisms both produce a
continuous range of wavelengths. A diffraction
Which type of
grating produces a uniform separation of
monochromator
wavelengths. A prism produces much better
produces the purest
separation of high-frequency light because
monochromatic light in
refraction is greater for higher-energy wavelengths.
the UV range?
Instruments using a prism and a variable exit slit can
produce UV light of a very narrow bandpass. The
adjustable slit is required in order to allow sufficient
light to reach the detector to set 100%T.
, 5-nm bandpass
Which monochromator
specification is required Bandpass refers to the range of wavelengths
in order to measure the passing through the sample. The narrower the
true absorbance of a bandpass, the greater the photometric resolution.
compound having a Bandpass can be made smaller by reducing the
natural absorption width of the exit slit. Accurate absorbance
bandwidth of 30 nm? measurements require a bandpass less than one-
fifth the natural bandpass of the chromophore.
Photomultiplier tube
The photomultiplier tube uses dynodes of
Which photodetector is increasing voltage to amplify the current produced
most sensitive to low by the photosensitive cathode. It is 10,000 times as
levels of light? sensitive as a barrier layer cell, which has no
amplification. A photomultiplier tube requires a DC-
regulated lamp because it responds to light
fluctuations caused by the AC cycle.
Dispersion from second-order spectra
Stray light is caused by the presence of any light
Which condition is a
other than the wavelength of measurement reaching
common cause of stray
the detector. It is most often caused by second-
light?
order spectra, deteriorated optics, light dispersed
by a darkened lamp envelope, and extraneous room
light.
Verified Solutions 100% Verified
Terms in this set (530)
Which formula correctly D
describes the relationship
between absorbance and
%T?
A. A = 2 - log %T
B. A = log 1/T
C. A = -log T
D. all of these options
A solution that has a 2.0
transmittance of 1.0 %T
would have an
absorbance of:
absorbance is directly proportional to
concentration
Beer's law states that A = a × b × c, where a is the
absorptivity coefficient (a constant), b is the path
In absorption
length, and c is concentration. Absorbance is
spectrophotometry:
directly proportional to both b and c. Doubling the
path length results in incident light contacting twice
the number of molecules in solution. This causes
absorbance to double, the same effect as doubling
the concentration of molecules.
,Which wavelength would 450 nm
be absorbed strongly by
a red-colored solution? A solution transmits light corresponding in
A. 450 nm wavelength to its color, and usually absorbs light of
B. 585 nm wavelengths complementary to its color. A red
C. 600 nm solution transmits light of 600-650 nm and strongly
D. 650 nm absorbs 400-500 nm light.
525 nm
A green-colored solution
would show highest Green light consists of wavelengths from 500-550
transmittance at: nm. A green-colored solution with a transmittance
A. 475 nm maximum of 525 nm and a 50-nm bandpass
B. 525 nm transmits light of 525 nm and absorbs light below
C. 585 nm 475 nm and above 575 nm. A solution that is green
D. 620 nm would be quantitated using a wavelength that it
absorbs strongly, such as 450 nm.
,SITUATION: A Replace the source lamp
technologist is
performing an enzyme Visible spectrophotometers are usually supplied
assay at 340 nm using a with a tungsten or quartz halogen source lamp.
visible-range Tungsten lamps produce a continuous range of
spectrophotometer. After wavelengths from about 320-2,000 nm. Output
setting the wavelength increases as wavelength becomes longer peaking at
and adjusting the readout around 1,000 nm, and is poor below 400 nm. As the
to zero %T with the light lamp envelope darkens with age, the amount of
path blocked, a cuvette light reaching the photodetector at 340 nm
with deionized water is becomes insufficient to set the blank reading to
inserted. With the light 100%T. Quartz halogen lamps produce light from
path fully open and the 300 nm through the infrared region. Deuterium or
100%T control at hydrogen lamps produce ultraviolet-rich spectra
maximum, the instrument optimal for ultraviolet (UV) work. Mercury vapor
readout will not rise lamps produce a discontinuous spectrum that
above 90%T. What is the includes a high output at around 365 nm that is
most appropriate first useful for fluorescent applications. Xenon lamps
course of action? generate a continuous spectrum of fairly uniform
A. Replace the source intensity from 300-2,000 nm, making them useful for
lamp both visible and UV applications.
B. Insert a wider cuvette
into the light path
C. Measure the voltage
across the lamp terminals
D. Replace the instrument
fuse
A prism and a variable exit slit
Diffraction gratings and prisms both produce a
continuous range of wavelengths. A diffraction
Which type of
grating produces a uniform separation of
monochromator
wavelengths. A prism produces much better
produces the purest
separation of high-frequency light because
monochromatic light in
refraction is greater for higher-energy wavelengths.
the UV range?
Instruments using a prism and a variable exit slit can
produce UV light of a very narrow bandpass. The
adjustable slit is required in order to allow sufficient
light to reach the detector to set 100%T.
, 5-nm bandpass
Which monochromator
specification is required Bandpass refers to the range of wavelengths
in order to measure the passing through the sample. The narrower the
true absorbance of a bandpass, the greater the photometric resolution.
compound having a Bandpass can be made smaller by reducing the
natural absorption width of the exit slit. Accurate absorbance
bandwidth of 30 nm? measurements require a bandpass less than one-
fifth the natural bandpass of the chromophore.
Photomultiplier tube
The photomultiplier tube uses dynodes of
Which photodetector is increasing voltage to amplify the current produced
most sensitive to low by the photosensitive cathode. It is 10,000 times as
levels of light? sensitive as a barrier layer cell, which has no
amplification. A photomultiplier tube requires a DC-
regulated lamp because it responds to light
fluctuations caused by the AC cycle.
Dispersion from second-order spectra
Stray light is caused by the presence of any light
Which condition is a
other than the wavelength of measurement reaching
common cause of stray
the detector. It is most often caused by second-
light?
order spectra, deteriorated optics, light dispersed
by a darkened lamp envelope, and extraneous room
light.
