Question 1
Identify which of the following is not a transmission line?
A. Telephone lines
B. Power transmission
C. Underground cables
D. Cavity resonators
View Answer
Answer: D
Explanation: The types of transmission line are telephone lines, power transmission lines, underground cables, coaxial cables, fibre optic cable transmission etc. Cavity resonators are not transmission lines, they are components that aid maximum transmission.
Question 2
The open wire transmission line consists of
A. Conductor
B. Dielectric
C. Both conductor and dielectric
D. Either conductor or dielectric
View Answer
Answer: C
Explanation: The open wire is a common form of transmission line. The open wire consists of conductors. The conductors of such lines are considered to be parallel and separated by a dielectric.
Question 3
Telephone lines and power lines are open wire transmission lines. State true/false.
A. True
B. False
View Answer
Question 4
The cable transmission line consists of
A. Conductors
B. Insulators
C. Insulated conductors
D. Insulated conductors with dielectric
View Answer
Answer: D
Explanation: The cable lines are underground transmission lines. The line consists of hundreds of individual paper insulated conductors twisted in pairs and combined inside a protective lead or plastic sheath, which is usually a solid dielectric.
Question 5
The coaxial cable consists of
A. Conductors
B. Insulators
C. Conductor with dielectric
D. Two conductors with dielectric
View Answer
Answer: D
Explanation: The coaxial cable consists of a hollow conductor and the second conductor is located inside and coaxial with the tube. The dielectric may be solid or gaseous.
Question 6
The coaxial cable are used in
A. Telephone cables transmission
B. Power transmission
C. Television signal transmission
D. Short wave transmission
View Answer
Answer: C
Explanation: Practically, the coaxial cables are employed in the transmission of the television signals from the dish antenna to the transponder.
Question 7
Identify which is not a type of waveguide.
A. Rectangular
B. Circular
C. Cylindrical
D. Cavity resonator
View Answer
Answer: D
Explanation: Rectangular waveguide is a commonly used waveguide. Cylindrical and circular waveguides are the same. Cavity resonator is not a waveguide.
Question 8
The range of frequencies handled by the waveguides is in
A. Hz
B. KHz
C. MHz
D. GHz
View Answer
Question 9
The range of frequencies operated by the coaxial cables is in
A. Hz
B. KHz
C. MHz
D. GHz
View Answer
Question 10
The cut off frequency for waveguide operation is
A. 2 MHz
B. 6 GHz
C. 4 MHz
D. 6 MHz
View Answer
Answer: B
Explanation: The waveguides should be operated above the cut off frequency of 6 GHz. This will lead to effective power transmission. At a frequency below this, will lead to attenuation.
Question 11
The highest means of communication is
A. Internet
B. Telephone
C. Television
D. Radio
View Answer
Answer: A
Explanation: Though all the means of communication use the radio frequencies, the internet communication is the fastest. It involves email, voice message, video message etc. The telephone, television and radio use transmission lines for communication through radio frequencies, whereas the internet uses both wired and wireless means. Also it employs optic fibre, which uses light as the medium, since it is faster than the radio signals.
Question 12
In free space, the charge carriers will be
A. 0
B. 1
C. 100
D. Infinity
View Answer
Answer: A
Explanation: Free space is not a conductor. Thus the charge carrier in free space is assumed to be zero. But the free space consists of particles or ions that get ionized during conduction.
Question 13
In free space, which parameter will be unity?
A. Permittivity
B. Absolute permittivity
C. Relative permittivity
D. Permeability
View Answer
Answer: C
Explanation: The relative permittivity is a constant for a particular material. It is unity for free space or air. The absolute permittivity is a constant given by 8.854 x 10^-12 C/m2.
Question 14
Which parameter is unity in air medium?
A. Permittivity
B. Absolute permittivity
C. Relative permittivity
D. Permeability
View Answer
Answer: C
Explanation: In free space or air medium, the relative permeability is also unity, like relative permittivity. The absolute permeability is given by 4π x 10^-7 units.
Question 15
The conductivity in free space medium is
A. Infinity
B. Unity
C. Zero
D. Negative
View Answer
Answer: C
Explanation: As the charge carriers are not available in free space, the conductivity will be very low. For ideal cases, the conductivity can be taken as zero.
Question 16
Zero permeability/permittivity implies which state?
A. No ions are allowed in the medium
B. No current is generated in the medium
C. No magnetic or electric energy is permitted in the medium
D. No resistivity
View Answer
Answer: C
Explanation: The zero permittivity in an electric field refers to the ability of the field/medium to permit electric charges in it. Similarly, zero permeability in a magnetic field refers to the ability of the field/medium to permit the magnetic energy into the field.
Question 17
The intrinsic impedance of free space is
A. 489
B. 265
C. 192
D. 377
View Answer
Question 18
In free space, the condition that holds good is
A. Minimum attenuation and propagation
B. Minimum attenuation and maximum propagation
C. Maximum attenuation and minimum propagation
D. Maximum attenuation and propagation
View Answer
Answer: B
Explanation: The free space does not have any barrier for attenuation. Thus it enables minimum attenuation and maximum propagation. This technique is employed in line of sight communication.
Question 19
The vectors of the electromagnetic wave propagation can be expressed in
A. Dot product
B. Cross product
C. Unit vector
D. Perpendicular vector
View Answer
Answer: B
Explanation: In an EM wave, the electric and the magnetic fields will be perpendicular to each other and with the direction of the propagation. Thus it can be expressed in cross product where iE x iH = iw. Here iE is the electric vector component, iH is the magnetic vector component and iw is the vector of the wave propagating.
Question 20
The Snells law can be derived from which type of incidence?
A. Incidence angle
B. Reflected angle
C. Refracted angle
D. Oblique incidence
View Answer
Question 21
The expression for refractive index is given by
A. N = v/c
B. N = c/v
C. N = cv
D. N = 1/cv
View Answer
Answer: B
Explanation: The refractive index is defined as the ratio of the velocity of light in a vacuum to its velocity in a specified medium. It is given by n = c/v. It is constant for a particular material.
Question 22
Numerical aperture is expressed as the
A. NA = sin θa
B. NA = cos θa
C. NA = tan θa
D. NA = sec θa
View Answer
Answer: A
Explanation: The numerical aperture is the measure of how much light the fiber can collect. It is the sine of the acceptance angle, the angle at which the light must be transmitted in order to get maximum reflection. Thus it is given by NA = sin θa.
Question 23
For total internal reflection to occur, which condition must be satisfied?
A. N1 = N2
B. N1 > N2
C. N1 < N2
D. N1 x N2=1
View Answer
Answer: B
Explanation: The refractive of the transmitting medium should be greater than that of the receiving medium. In other words, the light must flow from denser to rarer medium, for total internal reflection to occur.
Question 24
Find the refractive index of a medium having a velocity of 1.5 x 10^8.
A. 0.5
B. 5
C. 0.2
D. 2
View Answer
Answer: D
Explanation: The refractive index is given by the ratio of the speed of light to the velocity in a particular medium. It is given by n = c/v. On substituting for v = 1.5 x 10^8 and c = 3 x 10^8, we get n = 3/1.5 = 2. The quantity has no unit.
Question 25
The refractive index of water will be
A. 1
B. 2.66
C. 5
D. 1.33
View Answer
Answer: D
Explanation: The velocity of light in water as medium will be 2.25 x 10^8. On substituting for the speed of light, we get refractive index as n = 3/2.25 = 1.33(no unit).
Question 26
The refractive index of air is unity. State True/False.
A. True
B. False
View Answer
Answer: A
Explanation: The velocity of light in the air medium and the speed of light are both the same. Since light travels at maximum velocity in air only. Thus the refractive index n = c/v will be unity.
Question 27
The numerical aperture of a material with acceptance angle of 60 degree in water will be
A. 1.15
B. 2.15
C. 5.21
D. 1.52
View Answer
Answer: A
Explanation: The numerical aperture is given by NA = n sin θa, where n is the refractive index. It is 1.33 for water medium. Given that the acceptance angle is 60, we get NA = 1.33 sin 60 = 1.15.
Question 28
The refractive index is 2.33 and the critical angle is 350. Find the numerical aperture.
A. 2
B. 1.9
C. 2.33
D. 12
View Answer
Answer: B
Explanation: The numerical aperture is given by NA = n cos θc, where θc is the critical angle and n is the refractive index. On substituting for n = 2.33 and θc = 35, we get NA = 2.33 cos 35 = 1.9(no unit).
Question 29
Choose the optical fibre material from the given materials.
A. Glass
B. Plastic
C. Silica
D. Quartz
View Answer
Answer: C
Explanation: Silica is the most dominant optical fibre material. This is because of its hardness, flexibility, melting point. Also it is an easily available material.
Question 30
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
View Answer
Answer: Option A
Explanation:
Velocity is a function of displacement. Phase velocity Vp is a measure of angular velocity.
Question 31
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
View Answer
Answer: Option A
Explanation:
The component of phase waves which is in x direction is reflected at the interference between the higher and lower refractive index media. It is assumed that such an interference forms a lowest order standing wave, where electric field is maximum at the center of the guide, decaying towards zero.
Question 32
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
View Answer
Answer: Option C
Explanation:
Total internal reflection takes place when the light wave is in the more dense medium and approaching towards the less dense medium. Also, the angle of incidence is greater than the critical angle. Critical angle is an angle beyond which no propagation takes place in an optical fiber.
Question 33
What is refraction?
A. Bending of light waves
B. Reflection of light waves
C. Diffusion of light waves
D. Refraction of light waves
View Answer
Answer: Option A
Explanation:
Unlike reflection, refraction involves penetration of a light wave from one medium to another. While penetrating, as it passes through another medium it gets deviated at some angle.
Question 34
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
View Answer
Answer: Option A
Explanation:
In the above equation, k = 2Π/λ, also termed as wave equation, k gives us the direction of propagation and also the rate of change of phase with distance. Hence it is termed as phase propagation constant.
Question 35
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
View Answer
Answer: Option A
Explanation:
Electromagnetic mode theory finds its basis in electromagnetic waves. Electromagnetic waves are always represented in terms of electric field E, magnetic field H, electric flux density D and magnetic flux density B. These set of equations are provided by Maxwell’s equations.
Question 36
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
View Answer
Answer: Option B
Explanation:
Group velocity is much important in relation to transmission characteristics of optical fiber. This is because the optical wave propagates in groups or form of packets of light.