ASM 275 TEST PAPER 2026 FULL SOLUTION
VERIFIED
◉ basic components of a spectrophotometer. Answer: -source of
radiant energy (light source)
-monochromator
-sample container (cuvette)
-detector system
-readout device
◉ types of spectrophotometric light sources. Answer: -tungsten
-deuterium
-LASER
◉ tungsten (light source). Answer: -360-1000nm
-visible to infrared (HOT)
-gets very hot and cooks the analyte (causes a false increase in the
concentration)
◉ deuterium (light source). Answer: -less than 360nm
-ultraviolet
,◉ LASER (light source). Answer: -light amplification by stimulated
emission of radiation
-based on interaction of radiant energy (wavelength) and specific
excited atoms or molecules
-laser light has a narrow spectral width = INCREASES the specificity
◉ considerations of spectrophotometric light sources. Answer: -
wavelength range (depends on what analyte is being studied)
-spectral distribution within range
-stability of light source
-temperature
◉ monochromator function. Answer: -isolate individuals
wavelengths
-not a single 'color' but a narrow bandpass (width)
-ex: monochromator with 20nm bandpass, set wavelength to
400nm, wavelength is measured from +/-20nm band width = actual
measurement is 390-410nm
◉ monochromator effectiveness. Answer: -type of monochromator
used
-width of entrance and exit slits
-big slit = more light passes through
-small slit = less light passes through
,◉ types of monochromators. Answer: -glass filter
-interference filters
-glass prism
-diffraction grating
◉ glass filter (monochromator). Answer: -colored glass
-bandpass about 50nm wide of radiant energy
-inexpensive, scratch and break easily
-can slide in easily and pull out
◉ interference filter (monochromator). Answer: -monochromatic
light is produced by constructive interference of radiant energy
-isolates the wavelength it was by interfering with the other
wavelengths that it doesn't want
-sets of mirrored surfaces allows the radiant energy to travel back
and forth between them, reinforcing the desired wavelength
-bandpass 5-10nm (narrow)
◉ glass prism (monochromator). Answer: -non-linear, curved
spectrum produced
-can work with a curved spectrum but it is difficult to isolate a
wavelength
, -rotated to allow desired wavelength through entrance slit
◉ diffraction grating (monochromator). Answer: -parallel grooves
-linear, straight spectrum produced
-a lot easier to work with inside the instrument
-principle that light bends when passing a corner
-light bends when it hits the edge
-degree of bending depends on the wavelength
-bandpass can be less than 1nm
-MOST PREFERRED method because it is so specific
◉ sample container - cuvette**. Answer: -light path: Lambert's Law
(A=abc, remains constant)
-shape: round, square, flow-through
-material: plastic (OK but is cheap and can scratch), glass (visible
range), quartz (UV region)
◉ photodetector. Answer: converts light energy (photons) into
electrical energy
◉ phototube. Answer: -when the negative electrons are exposed to
light, they jump to the anode
VERIFIED
◉ basic components of a spectrophotometer. Answer: -source of
radiant energy (light source)
-monochromator
-sample container (cuvette)
-detector system
-readout device
◉ types of spectrophotometric light sources. Answer: -tungsten
-deuterium
-LASER
◉ tungsten (light source). Answer: -360-1000nm
-visible to infrared (HOT)
-gets very hot and cooks the analyte (causes a false increase in the
concentration)
◉ deuterium (light source). Answer: -less than 360nm
-ultraviolet
,◉ LASER (light source). Answer: -light amplification by stimulated
emission of radiation
-based on interaction of radiant energy (wavelength) and specific
excited atoms or molecules
-laser light has a narrow spectral width = INCREASES the specificity
◉ considerations of spectrophotometric light sources. Answer: -
wavelength range (depends on what analyte is being studied)
-spectral distribution within range
-stability of light source
-temperature
◉ monochromator function. Answer: -isolate individuals
wavelengths
-not a single 'color' but a narrow bandpass (width)
-ex: monochromator with 20nm bandpass, set wavelength to
400nm, wavelength is measured from +/-20nm band width = actual
measurement is 390-410nm
◉ monochromator effectiveness. Answer: -type of monochromator
used
-width of entrance and exit slits
-big slit = more light passes through
-small slit = less light passes through
,◉ types of monochromators. Answer: -glass filter
-interference filters
-glass prism
-diffraction grating
◉ glass filter (monochromator). Answer: -colored glass
-bandpass about 50nm wide of radiant energy
-inexpensive, scratch and break easily
-can slide in easily and pull out
◉ interference filter (monochromator). Answer: -monochromatic
light is produced by constructive interference of radiant energy
-isolates the wavelength it was by interfering with the other
wavelengths that it doesn't want
-sets of mirrored surfaces allows the radiant energy to travel back
and forth between them, reinforcing the desired wavelength
-bandpass 5-10nm (narrow)
◉ glass prism (monochromator). Answer: -non-linear, curved
spectrum produced
-can work with a curved spectrum but it is difficult to isolate a
wavelength
, -rotated to allow desired wavelength through entrance slit
◉ diffraction grating (monochromator). Answer: -parallel grooves
-linear, straight spectrum produced
-a lot easier to work with inside the instrument
-principle that light bends when passing a corner
-light bends when it hits the edge
-degree of bending depends on the wavelength
-bandpass can be less than 1nm
-MOST PREFERRED method because it is so specific
◉ sample container - cuvette**. Answer: -light path: Lambert's Law
(A=abc, remains constant)
-shape: round, square, flow-through
-material: plastic (OK but is cheap and can scratch), glass (visible
range), quartz (UV region)
◉ photodetector. Answer: converts light energy (photons) into
electrical energy
◉ phototube. Answer: -when the negative electrons are exposed to
light, they jump to the anode
