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The Brewster angle is expressed as
c Explanation: The tangent of the Brewster angle is the ratio of the refractive indices of the second medium to that of the first medium. It is given by tan θb= n2/n1. Thus the Brewster angle will be θb = tan-1(n2/n1).
c
See lessExplanation: The tangent of the Brewster angle is the ratio of the refractive indices of the second medium to that of the first medium. It is given by tan θb= n2/n1. Thus the
Brewster angle will be θb = tan-1(n2/n1).
The Brewster angle is valid for which type of polarisation?
b Explanation: The parallel polarisation of the electromagnetic waves is possible only when the transmission occurs at the Brewster angle.
b
See lessExplanation: The parallel polarisation of the electromagnetic waves is possible only
when the transmission occurs at the Brewster angle.
Choose the optical fibre material from the given materials.
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.
c
See lessExplanation: Silica is the most dominant optical fibre material. This is because of its
hardness, flexibility, melting point. Also it is an easily available material.
The refractive index is 2.33 and the critical angle is 350. Find the numerical aperture.
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).
b
See lessExplanation: 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).
The core refractive index should be lesser than the cladding refractive index for a coaxial cable. State True/False
b Explanation: The light should pass through the core region only, for effective transmission. When light passes through cladding, losses will occur, as cladding is meant for protection. Thus core refractive index must be greater than the cladding refractive index.
b
See lessExplanation: The light should pass through the core region only, for effective
transmission. When light passes through cladding, losses will occur, as cladding is
meant for protection. Thus core refractive index must be greater than the cladding
refractive index.
The numerical aperture of a material with acceptance angle of 60 degree in water will be
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.
a
See lessExplanation: 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.
Find the acceptance angle of a material which has a numerical aperture of 0.707 in air.
c Explanation: The numerical aperture is given by NA = n sin θa, where n is the refractive index. It is unity in air. Thus NA = sin θa. To get θ= sin-1 (NA), put NA = 0.707, thus θa = sin-1(0.707) = 45 degree.
c
See lessExplanation: The numerical aperture is given by NA = n sin θa, where n is the refractive index. It is unity in air. Thus NA = sin θa. To get θ= sin-1
(NA), put NA = 0.707, thus θa = sin-1(0.707) = 45 degree.
The numerical aperture of a coaxial cable with core and cladding indices given by 2.33 and 1.4 respectively is
d Explanation: The numerical aperture is given by NA = √(n12 – n22), where n1 and n2 are the refractive indices of core and cladding respectively. On substituting for n1 = 2.33 and n2 = 1.4, we get NA = √(2.332-1.42) = 1.86.
d
See lessExplanation: The numerical aperture is given by NA = √(n12 – n22), where n1 and n2 are the refractive indices of core and cladding respectively. On substituting for n1 = 2.33 and n2 = 1.4, we get NA = √(2.332-1.42) = 1.86.
The refractive index of air is unity. State True/False.
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.
a
See lessExplanation: 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.
The refractive index of water will be
d Explanation: The velocity of light in water as medium will be 2.25 x 108. On substituting for the speed of light, we get refractive index as n = 3/2.25 = 1.33(no unit).
d
See lessExplanation: The velocity of light in water as medium will be 2.25 x 108. On substituting for the speed of light, we get refractive index as n = 3/2.25 = 1.33(no unit).