Nanotechnology Questions and Answers – Nano-Optics – Meta Materials – Set 2

This set of Nanotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Nano-Optics – Meta Materials – Set 2”.

1. Pick the odd one out with respect to the application of metamaterials.
a) Metamaterial antenna – enhanced radiated power
b) Metamaterial absorber – counteract adverse effects of the seismic waves
c) Metamaterial superlens – resolution beyond diffraction limit
d) Metamaterial sound filters – improve ultrasound resolution
View Answer

Answer: b
Explanation: A metamaterial antenna makes use of metamaterial to improve its performance by enhancing the antenna’s radiated power. Metamaterial superlens uses metamaterial in order to achieve resolution beyond the diffraction limit. Seismic metamaterials are utilized in counteracting adverse effects of seismic waves on man – made structures. Metamaterial sound filters can control sound or light signals. They have the ability to improve ultrasound resolution and change a material’s colour.

2. What kind of metamaterials behave both as metals and dielectrics?
a) Double positive metamaterials
b) Acoustic metamaterials
c) Mechanical metamaterials
d) Hyperbolic metamaterials
View Answer

Answer: d
Explanation: Hyperbolic metamaterials have the ability to behave both as metals for certain polarization or direction of light propagation and as dielectrics for the others. These materials show extreme anisotropy which leads to directional propagation of light within and on their surface. They have shown potential applications in the field of sensing, imaging etc.

3. Split ring resonator is a metamaterial exhibiting artificial magnetism.
a) True
b) False
View Answer

Answer: a
Explanation: SSR or split ring resonator is the best example that can be cited when discussing metamolecules exhibiting artificial magnetism. SSR along with its derivative – a pair of concentric split – rings is known as a double split – ring resonator (DSSR). This can also exhibit artificial magnetism within a wide spectral range, spanning from microwave to IR frequencies.

4. Which factor is not responsible for controlling sound waves using acoustic metamaterials?
a) Mass Density
b) Tellegen parameter
c) Chirality
d) Bulk modulus
View Answer

Answer: b
Explanation: Acoustic metamaterials can control, direct and modify sound in the form of sonic, infrasonic or ultrasonic waves in different states of matter. These materials control the sound waves via bulk modulus ꞵ, mass density ρ and chirality. Bulk modulus and mass density are analogous to permittivity and permeability in electromagnetic metamaterials.

5. What causes the electromagnetic properties in metamaterials?
a) Response of atoms
b) Response of molecules
c) Response of base materials
d) Response of meta – atoms
View Answer

Answer: d
Explanation: Atomic or molecular level of base materials don’t determine the electromagnetic properties of metamaterials. However, they are determined by the configuration of their elementary building blocks. The newly designed structure comprising of metamolecules or meta – atoms provide unusual properties to the material.

6. Which of the following options best describe an electromagnetic bandgap metamaterial?
a) Microlattices are created using trusses
b) Control propagation of light
c) Corresponding Ꜫr and μr, both are positive
d) Control acoustic, elastic and seismic waves
View Answer

Answer: b
Explanation: Electromagnetic bandgap metamaterials (EBM or EBG) can control the propagation of light using photonic crystals (PCs) or (LHMs) left handed materials. These function by permitting light to propagate in specific, designed directions. The PCs and LHMs can be designed with bandgaps at desired frequencies. The period size of these metamaterials is a certain fraction of wavelength, creating constructive and destructive interference.

7. What is the physical significance of the negative sign for the refractive indices of metamaterials?
a) Either of Ꜫr or μr is negative
b) Snell’s law is not followed
c) Real parts of Ꜫr and μr are also negative
d) Antiparallel phase velocity of a wave
View Answer

Answer: d
Explanation: Negative index metamaterials have negative refractive index by virtue of the simultaneous negative permittivity and negative permeability. This negative sign is consistent with the laws of physics and has a physical significance indicating that the phase velocity of a wave is antiparallel to its group velocity.

8. A metamaterial absorber can be applied as a useful feature in which of the following?
a) Superlens
b) Cloaking device
c) Solar photovoltaics
d) Radar cross section
View Answer

Answer: c
Explanation: A metamaterial absorber finds its applications in the field of solar photovoltaics and photodetection. The absorber manipulates the loss of components of metamaterials’ permittivity and magnetic permeability. This is carried out to absorb larger amounts of electromagnetic radiation. These can also find applications in metamaterial cloaking and celestial mechanics but are often not used in these applications.

9. Who studied metamaterials for the first time?
a) David R.Smith
b) Jagadish Chandra Bose
c) Valerie Browning
d) Michael Faraday
View Answer

Answer: b
Explanation: The first ever metamaterial to be studied was by Sir Jagadish Chandra Bose in 1898. In his experiments, twisted jutes were placed between a spark generator equipped with a polarizer and a detector. This determined the orientation of the polarization plane of the transmitted waves upon rotating an analyzer before the detector. He was able to form twisted jute of two varieties, one with a positive while the other with a negative refractive index. He thus confirmed that the twisted structure produced an optical twist of the plane of polarization.

10. Choose the correctly matched pair from the following.
a) Hall metamaterials = Manipulate and direct sound waves in gases, liquids and solids
b) Chiral metamaterials = Provide crushability and light weight
c) Elastic metamaterials = Prevent propagation of certain wavebands of light
d) Bi – isotropic = Magnetoelectric coupling
View Answer

Answer: d
Explanation: Bi – isotropic metamaterials showcase magnetoelectric coupling. Acoustic metamaterials are responsible for regulating and manipulating sound waves in different states of matter – solids, liquids and gases. Structural metamaterials exhibit properties such as lightweight and crushability. Electromagnetic bandgap materials help prevent the propagation of certain wavebands of light.

11. What is the size range of metamolecules?
a) λ0/6 – λ0/2
b) λ0/100 – λ0/50
c) λ0/20 – λ0/10
d) λ0/50 – λ0/30
View Answer

Answer: a
Explanation: In general, the typical size range of metamolecules lies between λ0/6 to λ0/2, which may slightly decrease by a factor of 1.5 to 2 owing to the high refractive index dielectric substances. The precise shape, size, geometry, orientation and arrangement of these materials give them their peculiar properties.

Sanfoundry Global Education & Learning Series – Nanotechnology.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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