Lenses and optical instruments


REAL-IS-POSITIVE CONVENTION All distances are measured from the optical centre. Distances of real objects and real images are positive. Distances of virtual objects and images are negative. The focal length of a converging lens is +ve (real focus). The focal length of a diverging lens is -ve (virtual focus).

Optical fibres in telecommunications

Optical fibres in telecommunications One application of optical fibres IS their increasing importance 1D telecommunications. Research is already far advanced and production of the necessary equipment has begun. It is expected that, by the end of the century, if not before, optical fibres will have largely replaced copper cables, not only for telephone conversations but also for transmitting pictures, …

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The eye

The eye Fig. 24.18 is a simplified diagram of the human eye. In many respects it is similar to the camera. It has a tough, white wall called the sclerotic of which the front portion, the cornea, is transparent. Situated in the aqueous humour in front of the eye lens is the iris orcoloured part of the eye …

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