Optics Answers

The fish swims 2 m below the flat surface of the lake. At what apparent depth below the surface is the fish for the observer directly above it on the surface of the lake? The refractive index of water is 1.33.

The radius of curvature of the concave mirror is 60 cm. At what distance from the mirror should the object be placed so that the rays that came from the object to the mirror are reflected from the mirror, and then travel parallel to each other?(answer:30 cm)

A nearsighted person cannot see clearly beyond 75 cm. What lens him

would you prescribe to correct his distance vision problem?

The refractive index of the core and cladding materials of an optical fibre is 1.46

and 1.38, respectively. Calculate the critical angle, numerical aperture and

acceptance angle at the air-fibre interface.

In a laser, the lasing levels are the first excited state and the ground state of the

active medium. If the energy of the first excited state is 1.5eV, calculate the

frequency of the laser light.

What are the advantages of using optical fibre as communication medium?

How is holography different from ordinary photography?

What is the difference between spontaneous emission of radiation and stimulated

emission of radiation?

Explain the meaning of coherence length.

What do you understand by spatial and temporal coherence?