Questions on chapter (Spectroscopy)
True and false: -
1- Beer's Law relates the amount of light absorbed by a sample to the
concentration of the absorbing species (
2- Emission is the process that consumes a photon and puts the atom or
molecule in an excited state.
M+ hv→ M* (
3- Absorption is the process that creates a photon and takes the the atom
or molecule in an excited state back to the ground state.
M* → M + hv )
4- The emitted photon has less energy than absorbed photon. (
5- The emission of electrons from the photoemissive cathode is triggered
by the impact of light. ()
6- The emitted electrons are attracted to electrode #1 (dynode 1), which
has a voltage that is 90V higher than the cathode. ()
7- The attraction of electrons to dynode 2 is due to its positive voltage,
which is 90V higher than dynode (
8- The process of electron emission and attraction continues until the
electrons reach the anode after passing through 9 dynodes. ()
9- The overall voltage difference between the anode and cathode is
900V()
10- Emission spectrum: hold the excitation wavelength steady and
measure the emission at various wavelengths (
11- Excitation spectrum: vary the excitation wavelength and vary the
wavelength measured for the emitted light(
12- Phosphorescence is always at shorter wavelength compared with
fluorescence
13- Phosphorescence is wider compared with fluorescence
14- Phosphorescence is stronger compared with fluorescence (
15- The MCT detector is a semiconductor, and the electrons present in it
absorb IR light and move from conduction band to valence band
16- Electrons from surface are accelerated towards secondary electrodes
called dynodes and gain enough energy to remove further electrons
(typically 4-12, to 50 with GaP). (
17- Wavelength Selector (monochromator): used to select many
wavelengths of light from the light source
18- Light Detector measures the amount of light passing through the
sample (
19- An instrument used to make absorbance or transmittance
measurements is known as a spectrophotometer(
20- When molecule absorbs light, triplet state has Higher energy than
singlet state(
21- When molecule absorbs light, Singlet to Triplet transition has a very
low probability (
22- When molecule absorbs light, Singlet to Singlet Transition is more
probable
23- Absorption of photon with sufficient energy to excite an electron will
also cause vibrational and rotational transitions
24- Excited vibrational and rotational states are Higher energy than
electronic state
25- transition between electronic states can occur between different
vibrational and rotational states (
26- fluorescence occurs at a longer wavelength than Phosphorescence
27- A diode is a pn junction, under forward bias, current flows from p-Si
to n-Si
28- p-type silicon has a ‘hole’ or electron vacancy – Al or B doped (
29- In photodiode array, Current which is necessary to restore the charge
cannot be detected
30- The detector detects the wavelength of light that has passed through
the sample.
Multiple choices; -
1- The unit scale of frequency is ______.
a) Sec-1
b) Hertz
c) Sec
d) A & B
2- ____ have quantized energy level and can absorb and emit photons
of energy equal to the difference in energy between two levels. a)
Atoms
b) Molecules
c) A & B
d) none of the above
3- What happens when light hits the photoemissive cathode?
a) Electrons are emitted
b) Protons are emitted
c) Photons are emitted
d) Neutrons are emitted
4- Where are the emitted electrons attracted after leaving dynode 1?
a) Dynode 2
b) Cathode
c) Anode
d) Photoemissive cathode
5- How many dynodes are involved in the electron amplification
process?
a) 1
b) 5
c) 9
d) 10
6- What is the typical range of electrons produced by one photon?
a) 10-100 electrons
b) 100-1000 electrons
c) 1,000-10,000 electrons
d) 10^6 - 10^7 electrons
6. Phosphorescence is _______wavelength compared with fluorescence
a) Longer, wider, weaker
b) Longer, narrower, weaker
c) Longer, narrower, stronger
d) All of above
7. Absorption is always on the ______wavelength compared to emission
a) longer
b) shorter
c) a &b
d) None of abo
8. Application(s) of MCT Photoconductive Mercury Cadmium Telluride
Detectors is/are ____
a) Thermal Imaging
b)CO2 Laser Detection
c)FTIR Spectroscopy
d)all of above
9. Main Optical spectrophotometer components are ______
a) Excitation sources
b) Monochromators
c) Detectors
d) all of above
10. _______ increases the signal so that it is easier to read against the
background noise
a) The lamp
b) The monochromator
c) The detector
d) The amplifier
11. ____________selects one wavelength and that wavelength is sent
through the sample.
a) The lamp
b) The monochromator
c) The detector
d) The amplifier
12. In Beer–Lambert’s law, c is the molar concentration, and its unit
is______
a) mol
b) mol/L
c) unitless
d) mol.L
13. The transition in a chromophore produces absorption at _______
a) different frequency ranges
b) specific frequency
c) wide range of frequencies
d) all of above
14. absorption is _______ to emission
a) mirrored relative
b) shorter wavelength compared
c) a and b
d) none of above
15. For photodiode array spectrophotometers, ___________
a) a white light passes through sample
b) The grating polychromator disperses the light into the component
wavelengths
c) - All wavelengths are measured simultaneously
d) all of above.
16. For photodiode array spectrophotometers, Resolution depends on
__________
a) the distance between the diodes
b) amount of dispersion
c) a and b
d) none of above
17. For photodiode array the more radiation that strikes, __________
a) the more charge remains
b) the less charge remains
c) no effect on charge
d) none of above
18. When a Molecule Absorbs Light, Relative rates of relaxation depends
on______
a) the molecule
b) the solvent
c) temperature and pressure
d) all of above
19. The more frequently used coefficient e(n) expressed in _____
a) mole
b) litre
c) kilometre
d) gram
20. Photodiode Array-multiplex and has __________sensitivity
a) High
b) Low
c) Moderate
d) we don’t know
21.For, Optical spectrophotometer, excitation source can be_______
a) prism
b) tungsten lamp
c) photodiode
d) slit
22. For, Optical spectrophotometer, detector can be_______
a) prism
b) tungsten lamp
c) photodiode
d) slit
23. For photomultiplier-single channel, to minimise noise it is necessary
to operate at the _________
a) Highest possible voltage
b) lowest possible voltage
c) zero voltage
d) none of above
24. For spectrophotometry, at high concentrations __________
a) Emission increases because absorption increases more rapidly
b) Emission decreases because absorption increases more rapidly c) a
and b
d) none of above
25.for spectrophotometer, current is______
a) amplified only
b) measured only
c) amplified and measured
d) minimized
