IA Flashcards
Basic design of
(i) single beam
(ii) double beam
(i) source (light)
entrance slit
dispersing device
exit slit
cuvette (sample holder)
detector
(ii) source (light) (uv-deuterium)
(visible- tungsten)
entrance slit
dispersing device
exit slit
cuvette (sample holder,
reference)
detector
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deuterium
- UV region (165-380nm)
- operate at high temperature
- a fused quartz, uv glass or
magnesium fluoride envelope
is used for casing
- run continuously for 1000
hrs
tungsten filament
- visible region (350-2000nm)
- effective (320-1100nm)
- broad frequencies
- need high temp to get high
light intensity and low
wavelength max
diffraction grating monochromator
- made of what?
-mlamda = b(sin i+ sin r)
-made of glass, quartz or alkyl halides
-the rays which are incident on the grating get reinforced with the reflected rays and cause the wavelength governed by the equation of
-mlamda = b(sin i+ sin r)
m-order
lamda-desired wavelength
b-grating spacing
i-angle of incidence
r-angle of diffraction
refractive type prism monochromator
- consists of what?
- entrance slit
- collimator lens
- prism
- focusing lens
- exit lens
prism monochromator
-function?
- separates the frequencies (V) from polychromatic light
-allows only certain wavelength to be selected and used
interference filters
- what is the function of interference filters?
- how does it works?
- used to select the wavelength more accurately by providing a narrow band pass around 10nm
- these filters rely on optical interference (destructive wave addition) to provide narrow bands of radiation
absorption filters
- manufactured from ?
- band widths are large or
small?
- what is the range of band
width?
- how does it works?
- manufactured from dyed glass
or pigmented gelatin resins - band widths are large
- range of band width is 20-
250nm - gelatin filters is constructed
by sandwitching a thin layer of
dyed gelatin of desired colour
between two thin glass plates
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filters
- absorption filters
- interference filters
monochromators
- prism
- refraction
- reflection
- grating
- diffraction
- transmission
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UV
- deuterium
- mercury arc
- halogen
- xenon discharge
Visible
- tungsten
-mercury vapour
light source
wavelength selector (monochromator)
sample holder
detector
light source
- creates a proper wavelength
- increase intensity
- easier to see absorbance
wavelength selector (monochromator)
- narrow band pass (select desired wavelength)
- increase intensity
sample holder
- fixed geometry
(pathlength b constant cm)
-increase intensity
detector
- stable
- sensitive to wavelength of interest
transmission type grating
-how
-lamda = d sin tehta /m
- refraction produce reinforcement
- wavelength of radiation produced by transmission grating can be expressed by lamda = d sin tehta /m
2 types of monochromator
- czerney-turner grating
- bunsen prism
important components
- entrance slit
- collimating lens or mirror -make the radiation parallel before hitting the dispersding element
- grating or prism
- focusing lens or mirror - to focus light of desired wavelength on exit slit
Grating
type of dispersion -
size -
stray light -
wavelength range of use -
Grating
type of dispersion - uniform dispersion
size - smaller
stray light - higher stray light (can be removed by filter)
wavelength range of use - unlimited
prism
type of dispersion -
size -
stray light -
wavelength range of use -
Prism
type of dispersion - shorter wavelength better separated
size - larger
stray light - less problem
wavelength range of use - limited (wavelength > 350nm) (glass will absorb <= 350nm)
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-barrier layer cells
-photo emissive cell detector
-photomultiplier
