# Nanotechnology Questions and Answers – Nano-Optics – Computational Electromagnetics

This set of Nanotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Nano-Optics – Computational Electromagnetics”.

1. Select from the given options a method not used to solve real life electromagnetic problems.
a) Interface method
b) Moment method
c) Finite Element method
d) Monte Carlo method

Explanation: Computational electromagnetics involves the use of numerical techniques to solve real-life electromagnetic problems. These techniques include method of moments or moment method, finite element method, Monte Carlo method, method of lines etc. However, interface method is a method used in computer programming languages.

2. Identify the computational technique that uses discrete Fourier or Chebyshev transforms for solving electric field vectors.
a) FVTD
b) PSTD
c) DGTD
d) PEEC

Explanation: Pseudo – spectral time domain is a computational technique that applies either discrete Fourier or discrete Chebyshev transforms to determine the spatial derivatives of the magnetic and electric field vectors that remain arranged in 2D or 3D lattice of unit cells. PSTD allows modeling of problems of greater size as there is the occurrence of negligible numerical phase velocity anisotropy errors compared to FDTD.

3. What is the method of moments also known as?
a) Coupled dipole approximation
b) Fast multipole method
c) Plane wave time domain
d) Boundary element method

Explanation: The method of moments is commonly known as the boundary element method (BEM) . It is a computational logic for solving linear partial differential equations which can be formulated in boundary integral form. It involves the evaluation of only boundary value rather than values throughout the space.

4. Select a software from the given options that is not based on finite element method.
a) COMSOL
b) MEEP
c) HFFS
d) MaxFem

Explanation: MEEP, the acronym for MIT Electromagnetic Equation Propagation, is an open-source software. It was first introduced in 2006. It incorporates the FDTD, finite difference time-domain method for designing and evaluating different electromagnetic problems.

5. Discontinuous Galerkin time domain (DGTD) method unifies the advantages of both (FVTD) and (FETD) methods.
a) True
b) False

Explanation: Discontinuous Galerkin time domain (DGTD) method incorporates the benefits of both the (FVTD) and (FETD) method. Similar to FVTD, operations of DGTD are localized and easily parallelizable. DGTD makes use of unstructured mesh and has high-order accuracy for high-order hierarchical basis function, resembling FETD.

6. Which computational method divides solution region into non-overlapping elements?
a) FDTD
b) FIT
c) FETD
d) FEM

Explanation: The finite element method (FET) is applied for solving partial differential equations in two or three space variables. The technique divides solution region into non-overlapping meshes. This can be achieved by a definite space discretization in the space dimensions that can be executed by the construction of mesh, the numerical domain for the solution that has finite number of points.

7. Pick the correct option from the following.
a) Eigenmode expansion solves Maxwell’s equation both in 2D and 3D
b) UTD solves electromagnetic scattering problems only in a single dimension
c) Eigenmode is less beneficial compared to FDTD method
d) UTD approximates far field electromagnetic fields as quasi optical

Explanation: Eigenmode expansion (EME) is a method that is used to solve Maxwell’s equations in 2D and 3D. This method is way more beneficial than FDTD method. Uniform theory of diffraction (UTD) , on the other hand, solves electromagnetic scattering problems in more than one dimension at the same point. It approximates near field electromagnetic fields as quasi-optical.

8. Identify a method that was proposed in 1977 by Thomas Weiland.
a) FIT
b) PWTD
c) MoM
d) FMM

Explanation: Thomas Weiland in the year 1977 proposed the finite integration technique (FIT) . The method deals with electromagnetic field problems in the time and frequency domain. It is a constant discretization scheme for the Maxwell’s equations in the integral form. The method includes the full range of electromagnetics and optical application.

9. Which method of computational electromagnetics solves equations in a cyclic manner?
a) BEM
b) FDTD
c) MoM
d) PEEC

Explanation: The method of finite difference time-domain (FDTD) involves the simple discretization of Maxwell’s equation in the differential form. The equations are solved in a cyclic manner such as the electric field being solved at a given instant followed by magnetic field at the next instant. This process is repeated several times to obtain the solution.

10. Find out a method from the given options that is used to accelerate MoM.
a) FIT
b) DDA
c) PWDT
d) MNA

Explanation: The plane wave time domain (PWTD) algorithm was introduced by Ergin, Shanker and Michielssen in the year 1998. The PWTD, apart from the FMM method, can be used to accelerate MoM solutions of integral equations involving the retarded potential.

11. UTD and UAT have been adopted to evaluate terrain effects and applied to the ILS glide-path problems.
a) True
b) False

Explanation: The instrument landing system (ILS) delivers the pilot with steering information for a smooth, accurate and controlled take off and landing. These informations help the pilot to steer through even the worst of weather conditions. The ILS system comprises of the localizer, glide path and marker beacons. UTD (uniform theory of diffraction) and UAT (uniform asymptotic theory) can be used to determine the terrain effects, for proper functioning of ILS.

12. Choose the incorrect statement from the following options with respect to partial element equivalent circuit (PEEC) .
a) Half spectrum method, valid from dc to minimum frequency
b) Integral equation is interpreted as Kirchoff’s voltage law
c) SPICE type circuit elements can be easily included
d) PEEC method has non-orthogonal geometrics included in it

Explanation: PEEC is a full spectrum technique valid from dc to the maximum frequency. This method considers the integral equation as Kirchoff’s voltage law. Equivalent circuit formulation includes SPICE type circuit elements. In this method models and analysis are based on both frequency and time domains. The PEEC method has been modified lately to incorporate the non-orthogonal geometries.

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