4. Light emission Flashcards
What does Emission mean?
Emission means to give off something, in our case light.
How can prism and optical grating participate in emission?
Prism or optical grating is used to decompose light emerging from the light source into its emission spectrum.
What is MONOCHROMATOR?
an optical component that selects a narrow wavelength range from the incident light by using either…
- dispersion on a prism
- or diffraction on an optical grating.
The entrance slit, prism or optical grating and exit slit are altogether called the __.
monochromator
Fill the gap
light intensity depends on the ___ (which device?), thus the corresponding width of the wavelength interval
width of the slit → The greater the slit-width, the greater the intensity
The role of The detector
It produces electric current proportional to intensity of light passing through the emission slit.
What is EMISSION SPECTRUM:?
emitted light intensity (J ) versus wavelength ().
→ It may be continuous, band or line spectrum
3 types of emission spectra
→ It may be continuous, band or line spectrum
Describe the spectrum produced by a prism
The spectrum produced by a prism is not linear, as dispersion is a nonlinear function of the wavelength.
Describe the spectrum produced by an optical grating
→ What is the disadvantage
has a linear wavelength dependence and hence a linear wavelength scale (Fig.3).
(The disadvantage of the grating over the prism is its low light utilization efficiency.)
Disadvantage of optical grating over prism
The disadvantage of the grating over the prism is its low light utilization efficiency.
What is the source of thermal radiation?
the thermal motion of the atoms, molecules, as they all have charges inside.
What is thermal radiation?
Electromagnetic radiation generated by the thermal motion of particles in matter.
Every material having nonzero absolute temperature (T> 0) emits___
thermal radiation
material having ___ emits thermal radiation.
nonzero absolute temperature (T> 0)
What is LUMINESCENT RADIATION?
when energy of the radiation is provided by transition of electrons from the excited state to the ground state.
3 ways to excite atoms and molecules
- by heating (thermo- luminescence, see flame photometer)
- by electric field (electro-luminescence, Hg vapor lamps)
- by radiation of higher energy visible or UV light (photoluminescence), etc.
The role of spectrometer
device that registers emission spectra by plotting the intensity versus wavelength graph.
How does a SPECTROMETER work?
Light from the light source enters through the entrance slit into the monochromator, where an optical grating decomposes it into its wavelength components.
→ The optical grating is rotated by a motor, thus different parts of the spectrum fall onto the exit slit.
→ The intensity of light selected by the slit is measured by a photodetector (photomultiplier or photodiode).
→ Primary electric current of the detector is amplified by the amplifier and is recorded by the X -Y plotter.
- SPECTROMETER
Light from the (1)___ enters through the (2)___ into the (3)___, where an (4)___ decomposes it into its wavelength components.
→ The (5)___ is rotated by a motor, thus different parts of the spectrum fall onto the (6)___.
→ The intensity of light selected by the slit is measured by a (7)___ (photomultiplier or photodiode).
→ Primary electric current of the detector is amplified by the (8)___ and is recorded by the (9)___
- light source
- entrance slit
- monochromator
- optical grating
- optical grating
- exit slit
- photodetector
- amplifier
- X -Y plotter.
- SPECTROMETER
Light from the (1)___ enters through the (2)___ into the (3)___, where an (4)___ decomposes it into its wavelength components.
→ The (5)___ is rotated by a motor, thus different parts of the spectrum fall onto the (6)___.
→ The intensity of light selected by the slit is measured by a (7)___ (photomultiplier or photodiode).
→ Primary electric current of the detector is amplified by the (8)___ and is recorded by the (9)___
- light source
- entrance slit
- monochromator
- optical grating
- optical grating
- exit slit
- photodetector
- amplifier
- X -Y plotter.
- SPECTROMETER
Light from the light source enters through the entrance slit into the monochromator, where an optical grating (1)___
→ The optical grating is (2)____, thus (3)___ fall onto the exit slit.
→ (4)____ selected by the slit is measured by a photodetector (photomultiplier or photodiode).
→ (5)___ is amplified by the amplifier and is recorded by the X -Y plotter.
- decomposes it into its wavelength components.
- rotated by a motor
- different parts of the spectrum
- The intensity of light
- Primary electric current of the detector
What is FLAME PHOTOMETER:?
A device in which the emission spectrum is produced after thermal excitation (by heating with a flame).
→ It is typically used for the determination of alkali metal concentration of solutions.
FLAME PHOTOMETER
The energy required for the excitation of the atoms is provided by the ___
→ The equipment used in the measurement is used for the simultaneous determination of ___
- the high temperature of the flame
- Na, K, or Li concentrations of urine or blood plasma.
FLAME PHOTOMETER
The sample solution is atomized with compressed air and___directly into the __
- sprayed as an aerosol
- flame of the burner
FLAME PHOTOMETER
Light emitted by the thermally excited alkali metal atoms passes through a (1)____ with transmissions corresponding to (2)___
- set of different band filters
- the characteristic wavelength ranges of Na, K and Li.
FLAME PHOTOMETER
Emitted light intensity, which is proportional to the concentration is detected by ___ that generate a corresponding electrical signal.
photosensors (photodiode)
FLAME PHOTOMETER
(1)___ which is proportional to the concentration is detected by photosensors (photodiode) that generate (2)___.
→ (3)___ amplify these signals, and the relative concentration values (e.g., in mmol/l) are displayed.
- Emitted light intensity,
- a corresponding electrical signal
- Amplifiers
FLAME PHOTOMETER
The energy required for the excitation of the atoms is provided by the high temperature of the flame___
→ The equipment used in the measurement is used for the simultaneous determination of ___
- the high temperature of the flame
- Na, K, or Li concentrations of urine or blood plasma.
Light sources of different types.
- glow discharge bulb,
- high pressure sodium lamp,
- plasma globe,
- germicidal lamp and
- fluorescent coating.
Fill the gap
Fill the gap
