Tag: fibre optics basics

Questions Related to fibre optics basics

Light of different colours propagates through air :

physics option c: imaging fibre optics basics optical fibre the critical angle, total internal reflection and optical fibre

  1. with velocity of air

  2. with different velocity

  3. with velocity of sound

  4. with equal velocity

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Correct Option: D
Explanation:
  • The velocity of the light does not change in air it will be equal for all the colours
  • If there may some other medium like water etc velocity will be changed
  • But it remains equal in air
  • Hence the option D is the right answer

Which of the following is used in optical fibres?

physics option c: imaging fibre optics basics optical fibre the critical angle, total internal reflection and optical fibre

  1. Total internal reflection

  2. Scattering

  3. Diffraction

  4. Refraction

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Correct Option: A
Explanation:

In optical fibers total internal reflection property of light waves are used, so as to confine the light rays inside the fiber.

Optical fibres transmit light along its axis, by the process of :

physics option c: imaging fibre optics basics optical fibre the critical angle, total internal reflection and optical fibre

  1. total internal reflection

  2. refraction

  3. interference

  4. diffraction

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Correct Option: A
Explanation:

The side-wall of optical fibre provides total internal reflection of beam of light incident on it.

In an optical fibre during transmission of light

physics option c: imaging fibre optics basics optical fibre the critical angle, total internal reflection and optical fibre

  1. Energy increases.

  2. Energy decreases.

  3. No loss of propagation of energy takes place.

  4. Light partially reflects and refracts.

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Correct Option: C
Explanation:

Attenuation is a gradual loss int he intensity of any kind of flux through a medium .in telecommunication the attenuation affect the propagation of waves and signals. so during transmission of light through  an optical fiber optical and electrical attenuators cause the loss in transmission.

Which principle is the basis for the transmission of light through fiber optic cables even if the cable is bent?

physics option c: imaging fibre optics basics optical fibre the critical angle, total internal reflection and optical fibre

  1. Photoelectric effect

  2. Uncertainty principle

  3. Light diffraction

  4. Light polarization

  5. Total internal reflection

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Correct Option: E
Explanation:

Optical fibres are used to transmit light from one place to another along curved path so it does not matter even if the cable is bent.Optical fibre transmission is based on phenomenon of total internal reflection .We must remember that optical fibre does not bend light, instead light follows a zig-zag path.

A cutted diamond sparkles because of its:

physics option c: imaging fibre optics basics optical fibre the critical angle, total internal reflection and optical fibre

  1. high refractive index

  2. hardness

  3. emission of light by the diamond

  4. absorption of light by the diamond

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Correct Option: A
Explanation:

A cutted diamond sparkles because of its high refractive index. Because of high refractive index, the light suffers total internal reflections many times. that is why it sparkles.

The velocity of light in the core of a step index fibre is $2\times { 10 }^{ 8 }m/s$ and the critical angle at the core-cladding interfere is ${ 80 }^{ 0 }$. Find the numerical aperture and the acceptance angle for the fibre in air. The velocity of light in vacuum is $3\times { 10 }^{ 8 }m/s$.

physics option c: imaging fibre optics basics optical fibre the critical angle, total internal reflection and optical fibre
  1. 0.264; $75.{ 3 }^{ 0 }$
  2. 0.464; $45.{ 3 }^{ 0 }$
  3. 0.364; $25.{ 3 }^{ 0 }$
  4. 0.264; $15.{ 3 }^{ 0 }$
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Correct Option: D

The optical path of a monochromatic light is the same if it goes through $2.00$ cm of glass or x cm of ruby. If the refractive index of glass is $1.510$ and that of ruby is $1.760$ find the value of x is _______ cm?

physics option c: imaging fibre optics basics optical fibre the critical angle, total internal reflection and optical fibre

  1. $1.716$

  2. $1.525$

  3. $2.716$

  4. $2.525$

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Correct Option: A
Explanation:

We know optical path =Refractive index $\mu \times$ length $x$=constant

Therefore ${ \mu  } _{ glass }{ x } _{ glass }={ \mu  } _{ ruby }{ x } _{ ruby }\ { x } _{ ruby }=\dfrac { { \mu  } _{ glass }{ x } _{ glass } }{ { \mu  } _{ ruby } } =\frac { 1.51\times 2 }{ 1.76 } =1.716$

Consider telecommunication through optical fibres. Which of the following statements is NOT true? 

physics option c: imaging fibre optics basics optical fibre the critical angle, total internal reflection and optical fibre

  1. Optical fobres can be of graded refractive index

  2. Optical fibres are subjected to electromagnetic interference from outside

  3. Optical fibres have extremely low transmission loss

  4. Optical fibres may have homogeneous core with a suitable cladding

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Correct Option: B

Optical fibre, which is used in communication, works on which principle?

physics option c: imaging fibre optics basics optical fibre the critical angle, total internal reflection and optical fibre

  1. Dispersion

  2. Total Internal reflection

  3. Reflection

  4. Refraction

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Correct Option: B