Light Beam

View Light Beam

Presenter: Jonathan Hare

Published: March 2009

Age: 14-19 and upwards

Views: 1210 views

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Type: Lectures

Source/institution: Vega


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Light is reflected off a flexible shiny surface fixed to the end of a plastic tube. When one speaks into the tubes sound vibrations pass down the tube and make the surface vibrate. The reflected light is therefore sent off from the surface in a continuously changing set of angles depending on the loudness and frequencies of the voice. The light is said to have become modulated by the sound – we have put our voice on a sunbeam! Getting the sound back (demodulation of the light beam) is also very simple. A solar cell is attached to a speaker amplifier. As the light intensity is changing with the voice so the signal from the solar cell changes. When amplified and sent to a speaker (a device that turns voltage into sound) one hears the original voice again!

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