This set of Solid State Chemistry test focuses on “Sources of Background Radiation Fluorescence”.
1. The collision between air molecules and diffracted X-ray are the___________
a) Sources of background scattering
b) Sources of front reflection
c) Sources of diffraction
d) Sources of background irradiation
Explanation: The quality of an X-ray powder diffraction pattern is governed to a considerable extent by the level of background radiation which is present. Collisions between air molecules and diffracted X-ray beams are the sources of background scattering. For high quality Guinier focusing films it is worth while to evacuate the box containing the sample and film.
2. The fluorescent radiation is absorbed by placing a filter when__________
a) It is weak
b) It is strong
c) It is too much in quantity
d) It holds more energy
Explanation: Fluorescent occurs when the sample acts as a secondary source of X-rays. If the fluorescent radiation is weak it may be absorbed by placing a filter between the sample and detector, e.g. a strip of nickel foil placed over the film.
3. If the fluorescent radiation is strong then which of the following parameters to be used?
a) Changing the path length of the secondary beam
b) Changing the wavelength of the primary beam
c) Keeping the wavelength of the secondary beam constant
d) Changing the frequency of the secondary beam
Explanation: When the fluorescent radiation is strong then the wavelength of the primary beam is changed generally by replacing an X-ray tube containing a copper target by one with an iron or molybdenum target.
4. Fluorescent occurs when the radiation in the primary beam knocks out___________
a) Outer shell electrons
b) Inner shell electrons
c) Outer shell photon
d) Inner shell photon
Explanation: Fluorescent occurs when the radiation in the primary beam that is emitted by the copper target knocks out inner shell electrons within atoms of the sample. Electrons in the outer shells drop down to occupy empty levels in the inner shells and in so doing they emit their excess energy in the form of X-rays.
5. Fluorescent radiation produced by electrons depends on which of the following factors?
a) Concentration of the photon
b) Solubility of the sample
c) Atomic number of the atoms
d) Frequency of the radiation
Explanation: The inner shell electrons are knocked out and thus fluorescent radiation is produced, in this method fluorescent radiation depends on the atomic number of the atoms in the sample relative to that of the target material.
6. Cu Kα radiation of wavelength 1.5418 A˚, is generated by which of the following transition?
Explanation: 2p→1s electronic transition generates the Cu Kα radiation of wavelength 1.5418 A˚ and in order to create a vacant 1slevel in the first place, 1s→∞ ionization potential is needed and this energy difference corresponds to a wavelength for copper of1.3804 A˚.
7. Cu Kα radiation can ionize 1s electrons in which of the following elements?
Cu Kα radiation can ionize 1s electrons in cobalt and iron but not in nickel, helium and hydrogen. Because the ionization potentials of 1s electrons in nickel, cobalt and iron correspond to 1.4880, 1.6081 and 1.7433 A˚ and Cu Kα X-rays can ionize electrons in atoms whose ionization energy has a value corresponding to λ > 1.5418 A˚.
8. Lighter atoms _________
a) Fluoresce strongly
b) Fluoresce less strongly
c) Doesn’t Fluoresce
d) Fluoresce very very strongly
Explanation: Lighter atoms also fluoresce, but less strongly, since fluorescence is strongest when the incident radiation has a wavelength that is only slightly shorter than the absorption edge (=IP) of the atoms.
9. When the X-rays strike a sample then the X-rays of the same wavelength as the incident beam is re-emitted and this is known as____________
a) Modified radiation
b) Same radiation
c) Coherent radiation
d) Non coherent radiation
Explanation: When X-rays strike a sample two types of scattered rays are produced. In the first, the incident beam sets the electrons of the atoms into vibration, the X-rays of the same wavelength as the incident beam is re-emitted and are the characteristic diffracted radiation with which we are familiar. This is known as coherent, unmodified radiation.
10. Organic and organic based materials give which type of powder patterns?
a) Very good quality powder pattern
b) Very poor quality powder pattern
c) Doesn’t give powder pattern at all
d) High concentrated powder pattern
Explanation: Due to the combined effects of reduced diffracted intensity and increased background intensity, organic and organic-based (e.g. polymeric) materials give poor quality powdered patterns.
Sanfoundry Global Education & Learning Series – Solid State Chemistry.
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