Optics Answers

Explain what is meant by a graded index optical fiber, giving an expression for the possible refractive index profile. Using simple ray theory concepts, discuss the transmission of light through the fiber. Indicate the major advantage of this type of fiber with regard to multimode propagation.

Describe with the aid of simple ray diagrams: (a) the multimode step index fiber; (b) the single-mode step index fiber. Compare the advantages and disadvantages of these two types of fiber for use as an optical channel.

Define the normalized frequency for an optical fiber and explain its use in the determination of the number of guided modes propagating within a step index fiber. A step index fiber in air has a numerical aperture of 0.16, a core refractive index of 1.45 and a core diameter of 60 μm. Determine the normalized frequency for the fiber when light at a wavelength of 0.9 μm is transmitted. Further, estimate the number of guided modes propagating in the fiber.

A viewing screen is separate from double slit source by 1.2m the distance between the two slits is 0.03mm the second order bright fringe (m=2)is 4.5cm from the center line .(a) determine the wavelength of the light.(b) calculate the distance between adjaseet bright fringe

A small, unshaded lamp of brightness 400 candelas, which may be considered a point source of light, is placed 4 meters above the floor of a big hall. Find: 

A. the total luminous flux emitted by the source, and

B. the intensity of illumination on the floor directly below the lamp.

Calculate the optical invariant for a photographic objective with F = 50 mm. N = 2, field of view +26.6°.

Calculate the optical invariant for a photographic objective with F = 50 mm. N = 2, field of view +26.6°.

A parallel beam of light falls normally on one phase of a small angled glass prism. Part of the beam

is refracted at the second phase and is deviated through an angle of 1.8o

. Another part is reflected

at the second phase and emerges at the first making an angle of 9.2o

with the normal. Calculate:

(i) The refractive index of the glass.

(ii) The angle of the prism.

State and explain fermat's principle. Using this principle derive shell's law of refraction .

Skew rays are accepted into a large core diameter (compared with the wavelength of the transmitted 

light) step index fiber in air at a maximum axial angle of 42°. Within the fiber they change direction by 

90° at each reflection. Determine the acceptance angle for meridional rays for the fiber in air.