This has to be one of the most engaging classroom light demonstrations!
How to transmit sound from your phone on a visible light beam . . .
- Plug the torch into your mobile phone’s ear phone socket
- Activate the solar panel connected to a pre-amp and speaker
- Play a song on the phone and the sound will ride the light beam to the solar panel. Very cool!
What is in the kit?
- A flashlight transmitter
- A solar panel receiver with amplifier & speaker
- USB cable to charge the speaker
- Bulb-shaped flickering LED light
- Flickering RGB ball
- Sugar beads, mirror and clear jar
- Instruction sheet with 10 Demos you can do in your classroom
Required (not included): 2 x AA batteries (not rechargeable); 3 x AAA batteries; sound sources such as a mobile phone or MP3 player.
The kit reviewed online
How does this happen?
The light beam is modulated. Everyone knows about the AM and FM on their radio. AM being amplitude modulation and FM, frequency modulation. The radio uses radio waves as carrier beam but visible light waves can do the same, as all are electromagnetic waves and therefore can be ‘modulated’ to carry information.
Modulation is the changing of the amplitude or frequency of a wave so it is in synchronisation with the variations of a second signal. The carrier wave simply carries the information superimposed on it by the information signal. Its waveform undergoes a change – it gets “modulated” with the information signal.
The image on the right gives an indication of how AM works.
The sound signal can be from any electrical audio source. The variable sound signal is fed into the light (carrier) signal, and the intensity (or amplitude) of the light beam changes so it reflects the information from the sound signal. These flashlight changes are minute but are detected by the solar panel which in turn mirrors its output to the same pattern.
The sound signal is virtually riding on the back of the carrier beam and goes wherever the carrier beam goes!
Receiver On / Off Switching Information
How to adjust the output Volume