How do we put our voice on a light beam? Here Jonathan
demonstrates how sun light or torch light can be reflected off
of a flexible shiny surface fixed to the end of a plastic tube
and then when one speaks into the tube 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 and we could say that we have therefore 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! This video should be used with the
following article: Light Beam (Link below)