Optical Fiber

Q. The frequency of a light wave in a material is $2\times {10}^{14}\text{Hz}$ and wavelength is $5000\stackrel{\circ }{\text{A}}$. The refractive index of material will be

1. $1.33$
2. $1.40$
3. $1.50$
4. $3.0$

Q. If ${\epsilon }_0$ and ${\mu }_0$ are the electric permittivity and magnetic permeability in a free space, $\epsilon$ and $\mu$ are the corresponding quantities in a medium, the index of refraction of the medium is,

1. $\sqrt{\frac{{\epsilon }_0{\mu }_0}{\epsilon \mu }}$
   
2. $\sqrt{\frac{\epsilon \mu }{{\epsilon }_0{\mu }_0}}$
3. $\sqrt{\frac{{\epsilon }_0\mu }{\epsilon {\mu }_0}}$
4. $\sqrt{\frac{\epsilon }{{\epsilon }_0}}$

Q. An optical fibre consists of a core having refractive index ${\mu }_1$ surrounded by a cladding of refractive index ${\mu }_2$ $({\mu }_2<{\mu }_1)$. A beam of light enters from the air at an angle of $\alpha$ with the axis of the fibre. The highest value of $\alpha$ for which ray can be travelled through fiber is

1. ${\cos }^{-1}\sqrt{{\mu }_2^2-{\mu }_1^2}$
2. ${\sin }^{-1}\sqrt{{\mu }_1^2-{\mu }_2^2}$
3. ${\tan }^{-1}\sqrt{{\mu }_1^2-{\mu }_2^2}$
4. ${\cos }^{-1}\sqrt{{\mu }_1^2-{\mu }_2^2}$

Q. A ray of light passes through $4$ transparent media with refractive indices ${\mu }_1,{\mu }_2,{\mu }_3$ and ${\mu }_4$ as shown. The surface of all media are parallel. If the emergent ray $\text{CD}$ is parallel to the incident ray $\text{AB}$, we must have

1. ${\mu }_1={\mu }_2$
2. ${\mu }_2={\mu }_3$
3. ${\mu }_3={\mu }_4$
4. ${\mu }_1={\mu }_4$

Q. The optical path of a monochromatic light is the same, when it goes either through $2.00\text{cm}$ of glass or $2.25\text{cm}$ of water. If, the refractive index of water is $1.33$, what is the refractive index of glass?

1. $1.67$
2. $1.5$
3. $1.8$
4. $1.9$

Q. In figure , light refracts from material $1$ into a thin layer of material $2$, crosses that layer, and then is incident at the critical angle on the interface between materials $2$ and $3$. The angle $\theta$ is.

1. ${\sin }^{-1}\left(\frac{13}{15}\right)$
2. ${\sin }^{-1}\left(\frac{13}{16}\right)$
3. ${\cos }^{-1}\left(\frac{13}{15}\right)$
4. ${\cos }^{-1}\left(\frac{13}{16}\right)$

Q. What is the speed of light and wavelength in a medium having refractive index $\mu =1.5$, if the wavelength of light in air is $780\text{nm}$ ?

1. $2\times {10}^8\text{m/s}$ and $520\text{nm}$
2. $1.5\times {10}^8\text{m/s}$ and $520\text{nm}$
3. $2\times {10}^8\text{m/s}$ and $500\text{nm}$
4. $1.5\times {10}^8\text{m/s}$ and $500\text{nm}$

Q. A slab of transparent material is made as shown in the figure. The thickness of $C$ is twice the thickness of $B$. If the number of waves in $A$ is equal to the number of waves in combination of $B$ and $C$, then the refractive index of $B$ is

1. $1.33$
2. $1.8$
3. $1.6$
4. $1.4$

Q.

Figure shows a transparent hemisphere of radius 3.0 cm made of a material of refractive index 2.0.

(a) A narrow beam of parallel rays is incident on the hemisphere as shown in the figure. Are the rays totally reflected at the plane surface ?

(b) Find the image formed by the refraction at the first surface.

(c) Find the image formed by the reflection or by the refraction at the plane surface.

(d) Trace qualitatively the final rays as they come out of the hemisphere.

Q.

How does light polarize in the reflection?

Q. The attenuation in optical fiber is mainly due to

1. Absorption
2. Scattering
3. Neither absorption nor scattering
4. Both (a) and (b)

Q.

One day Chetan's mother developed a severe stomach ache all of a sudden. She rushed to the doctor who suggested for an immediate endoscopy test and gave an estimate of expenditure for the same. Chetan immediately contacted his class teacher and shared the information with her. The class teacher arranged for the money and rushed to the hospital. On realizing that Chetan belonged to a below average income group family, even the doctor offered concession for the test fee. The test was conducted successfully.
Answer the following questions based on the above information :
(a) Which principle in optics is made use of in endoscopy ?
(b) Briefly explain the values reflected in the action taken by the teacher.
(c) In what way do you appreciate the response of the doctor on the given situation ?

Q.

Incident ray and reflected ray can never travel along the same path.

1. True
2. False

Q. Describe the construction and working of an optical fiber. State its uses.

Q. What is the structure of Diamond?

Q. What is optical fiber? On what principle does it work?

Q. Which of the following is not a fundamental physical quantity?

Q. Assertion :Optical fibres make use of total internal reflection. Reason: Light undergoes successive total internal reflections as it moves through an optical fibre.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Both Assertion and Reason are incorrect

Q. (a) What is the structure of an optical fiber?
(b) What is the principle used for transmitting audio and video signals using optical fiber? Explain the principle.

Q. A silicon optical fibre with a core diameter large enough has a core refractive index of 1.50 and a cladding refractive index 1.47. Determine
(i) the critical angle at the core cladding interface,
(ii) the numerical aperture for the fibre
(iii) the acceptance angle in air for the fibre.

Q. Assertion (A): Propagation of light through an optical fibre is due to total internal reflection taking place at the core-cladding interface.
Reason (R) : Refractive index of the material of the core of the optical fibre is greater than that of air.

1. Both (A) and (R) are true but (R) is not the correct explanation of (A)
2. (A) is false and (R) is true
3. Both (A) and (R) are true and (R) is the correct explanation of (A)
4. (A) is true and (R) is false

Q. Name the physical principle on which the working of optical fibres is based.

Q.

Total internal reflection of light is possible when light enters from _________

Q. In a diffraction pattern for a small pin hole, if the size of hole is increased (1) Size of central bright increases (2) Intensity increases (3) Intensity decreases (4) Size of central bright remains same.

Q. Name the principle on the basis of which optical fibres work.

Q. In optical fiber, refractive index of inner part is $1.68$ and refractive index of outer part is $1.44$. The numerical aperture of the fibre is

1. 0.5653
2. 0.6653
3. 0.8653
4. 0.7653

Q. The refractive index of the core of an optical fiber is ${\mu }_2$ and that of the cladding is ${\mu }_1$. The angle of incidence on the face of the core so that the light ray just undergoes total internal reflection at the cladding is

1. $si{n}^{-1}\left(\frac{{\mu }_1}{{\mu }_2}\right)$
2. $si{n}^{-1}({\mu }_2-{\mu }_1)$
3. $si{n}^{-1}\left(\sqrt{{\mu }_2^2-{\mu }_1^2}\right)$
4. $si{n}^{-1}\left(\sqrt{{\mu }_1^2-{\mu }_2^2}\right)$

Q. A cutted diamond sparkles because of its:

1. emission of light by the diamond
2. absorption of light by the diamond
3. high refractive index
4. hardness

Q. ntThe optical path of monchromatic light is same if it goes through 4 cm of glass or 4.5 cm of water.if the R.Fof glass is 1.53, R.F of water?n

Q. What is fibre optics?