# Electromagnetic Mode Theory for Optical Propagation

This set of Optical Communications Interview Questions and Answers focuses on “Electromagnetic Mode Theory for Optical Propagation”.

1. Which equations are best suited for the study of electromagnetic wave propagation?
a) Maxwell’s equations
b) Allen-Cahn equations
c) Avrami equations
d) Boltzmann’s equations

2. When λ is the optical wavelength in vacuum, k is given by k=2Π/λ. What does k stand for in the above equation?
a) Phase propagation constant
b) Dielectric constant
c) Boltzmann’s constant
d) Free-space constant

3. Constructive interference occur when total phase change after two successive reflections at upper and lower interfaces is equal to? (Where m is integer)
a) 2Πm
b) Πm
c) Πm/4
d) Πm/6

4. When light is described as an electromagnetic wave, it consists of a periodically varying electric E and magnetic field H which are oriented at an angle?
a) 90 degree to each other
b) Less than 90 degree
c) Greater than 90 degree
d) 180 degree apart

5. A monochromatic wave propagates along a waveguide in z direction. These points of constant phase travel in constant phase travel at a phase velocity Vp is given by?
a) Vp=ω/β
b) Vp=ω/c
c) Vp=C/N
d) Vp=mass/acceleration

6. Which is the most important velocity in the study of transmission characteristics of optical fiber?
a) Phase velocity
b) Group velocity
c) Normalized velocity
d) Average velocity

7. What is refraction?
a) Bending of light waves
b) Reflection of light waves
c) Diffusion of light waves
d) Refraction of light waves

8. The phenomenon which occurs when an incident wave strikes an interface at an angle greater than the critical angle with respect to the normal to the surface is called as ____________
a) Refraction
b) Partial internal reflection
c) Total internal reflection
d) Limiting case of refraction