This set of Nanotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Characterization of Nanoparticles – Set 2”.
1. What is the full form of CLSM?
a) Computerized laser scanning microscopy
b) Concave lens scanner microscopy
c) Confocal laser scanning microscopy
d) Concurrent laser beam scanner microscopy
View Answer
Explanation: The expanded form of CLSM is Confocal laser scanning microscopy, also referred to as confocal microscopy. It is an optical imaging technique that increases the optical resolution and contrast of a micrograph. This type of microscope is employed in a large number of fields such as microbiology, cell biology, optics and crystallography.
2. Find out a method used for characterizing the size, shape and concentration of nanoparticles.
a) Spectroscopy
b) Neutron scattering
c) Scanning probe microscopy
d) X-ray diffraction
View Answer
Explanation: Spectroscopy is one of the significant methods of characterization of nanoparticles. It can measure the particles interaction with electromagnetic radiation as a function of wavelength. It is also useful for characterizing nanoparticles on the basis of their size, shape and concentration.
3. How can astigmatism be corrected in electromagnetic lenses?
a) Differing the axial planes perpendicular to each other
b) Using concave lens elements
c) Differing the focal lengths for different wavelengths
d) Using stigmators
View Answer
Explanation: Astigmatism in electromagnetic lens can arise due to different values in focal length of the lens in two axial planes perpendicular to each other. Astigmatism can be corrected in electromagnetic lens by using a constant stigmator field that can be adjusted by the microscope operator.
4. Define resolution.
a) Ratio of image size to object size
b) Alteration of the focal length
c) Ratio of object size to image size
d) Smallest separation between two points on a specimen
View Answer
Explanation: The resolution of a microscope is defined as the smallest distance between two small objects that can still be distinguished as separate objects or entities by the observer or camera system.
5. What is the effect observed in SEM during secondary electron imaging wherein certain parts of the image appear brighter than the rest?
a) Scooter effect
b) Criegee mechanism
c) Accordion effect
d) Shadowing effect
View Answer
Explanation: Shadowing contrast is very often noticed while imaging secondary electrons in SEM. While images appear to look down holes and over the hills, the signals from sample areas lying in the direct line-of-sight of the detector are higher than those from ‘unseen’ parts of the specimen. As a consequence, they appear brighter.
6. SNOM can only form topographic images and not optical images of samples.
a) True
b) False
View Answer
Explanation: Scanning near field optical microscopy abbreviated as SNOM is a surface scanning microscope that uses a probe for the same purpose. The tip to sample distance while scanning can be controlled using a feedback circuit. It is used to generate topographic images (the tip displacement images) as well as optical images of the sample.
7. Label the marked parts of a SEM.
a) i = Electron gun; iv = Scanning coils; vi = Electron, X-ray or light detector
b) iii = Anode; ii = Specimen; vii = Objective lens
c) v = Condenser lens; vi = Scanning coils; iii = Specimen
d) vii = Electron, x-ray or light detector; i = Anode; iv = Electron gun
View Answer
Explanation: In this given diagram of a SEM, the marked parts are labeled as -i) Electron gun, ii) Anode, iii) Condenser lens, iv) Scanning coils, v) Objective lens, vi) Secondary electron detector or Electron, x-ray and light detector, and vii) Specimen.
8. Mark the incorrect statement from the following.
a) Elastic scattering involves no transfer of energy during the process
b) Frequency of various scattering events depend upon the specimen thickness
c) Incident waves undergo changes in amplitude during scattering
d) Small-angle elastic scattering is incoherent in nature
View Answer
Explanation: When a beam of light interacts with matter, a part of it gets scattered. The frequency of various scattering events depends on the thickness of the specimen. During scattering there is a change in the amplitude and/or phase of the incident waves. Scattering can be both elastic and inelastic in nature. Elastic scattering has no energy transfer during its course. Usually, the small-angle elastic scattering is coherent while inelastic scattering is incoherent.
9. What is deBroglie wavelength of an electron being accelerated through a potential of 30V?
a) 2.24 Å
b) 300 Å
c) 5.23 Å
d) 74 Å
View Answer
Explanation: The deBroglie wavelength of an electron accelerated through a potential (V) is given by,
λ = h/(2meVe)½
Here, h = Plank’s constant = 6.626 × 10-34m2kg/3
me = mass of electron = 9.1 × 10-31kg
e = charge on electron = 1.602 × 10-19C
V = 30V
⸫ λ = (6.626 × 10-34)/√(2 × 30 × 1.602 × 10-19 × 9.1 × 10-31)
λ = 2.24 × 10-10m = 2.24Å
10. These primary electrons can undergo large deflections and exit the surface of specimen with high K.E. What are these known as?
a) Secondary electrons
b) deBroglie electrons
c) Auger electrons
d) Backscattered electrons.
View Answer
Explanation: Backscattered electrons are primary electrons that undergo deflections and exit the surface of the sample with almost negligible change in their high Kinetic energy. This act of scattering out of the specimen interaction volume is a result of elastic scattering interactions with specimen atoms.
11. Select the correct statement out of the given options.
a) f(θ) cannot describe the amplitude of X-rays that are elastically scattered by matter
b) f(θ) decreases with the increase in scattering angle
c) f(θ) possesses both unit and dimension
d) On average, the electron scattering amplitude is proportional to Z-4/5
View Answer
Explanation: The atomic scattering amplitude f(θ) describes the amplitude of X-rays or electrons that are elastically scattered by matter. This function decreases with increasing angle for X-rays or electrons. fx(θ) is a dimensionless number. fe(θ), is the electron scattering amplitude and is proportional to Z3/2.
12. Identify a similarity between electron optics and light optics.
a) Wavelength of accelerated electrons and wavelength of photons
b) Interaction of matter and electrons or photons
c) Careful preparation of specimens
d) Electric charge or electrons.
View Answer
Explanation: Electron optics differs from light optics in multiple ways such as the wavelength of electrons and photons, interaction of electrons and photons with matter and charge on the particles. However, they are also analogous to each other in the careful preparation of specimens, and their usage in various medical and science studies and research.
13. What type of scattering involves the excitation of collective, resonant oscillations by electrons?
a) Phonon scattering
b) Crompton scattering
c) Single – electron excitation
d) Plasmon scattering
View Answer
Explanation: In plasmon scattering, the incident electrons excite plasmons or collective resonant oscillations of the valence electrons of a solid. The energy loss in this case from the incident beam is 5-30 eV and the mean free path Ʌ is almost 100nm. This is a dominant scattering process in electron-solid interactions.
14. What information is deciphered from the low angle reflections in a powder diffractometer?
a) Thickness of the thin films
b) Microstresses and microstrains
c) Repeat distances
d) Superlattice wavelengths
View Answer
Explanation: Powder diffractometer is an important X-ray diffraction technique. The low angle reflections give us information about the thickness of the thin films and multilayers. We even get to know about the mean size and size distributions of scattering objects like colloids and macromolecules.
15. Which of the following is not a method of characterization of nanoparticles?
a) Microscopy
b) X-ray diffraction
c) Chromatography
d) Spectroscopy
View Answer
Explanation: There are several methods of characterization of nanoparticles. These include microscopy, X-ray diffraction and spectroscopy. However, chromatography, centrifugation and filtration techniques are used for the separation of nanoparticles on the basis of size or other physical properties. These processes are carried out before the characterization of the nanoparticles.
Sanfoundry Global Education & Learning Series – Nanotechnology.
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