41.6 MB (5.3 MB compressed)
3109 x 4676 pixels
26.4 x 39.6 cm ⏐ 10.4 x 15.6 in (300dpi)
PHILLIP HAYSON / SCIENCE PHOTO LIBRARY PHILLIP HAYSON / SCIENCE PHOTO LIBRARY
Fibre optics. Telephone handset and a cable containing optical fibres. A telephone works by converting sound waves into electrical signals. These signals are then converted back into sound by the receiving telephone. The increasing number of telephone calls has required the use of high- volume transmission equipment such as optical fibres. The telephone's electrical pulses are converted into light at an exchange and sent down optical fibres. The optical fibres have a core of flexible glass covered in a protective coating. The difference in the refractive indexes of the core and coating means that the cable internally reflects light with little absorption.
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