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Light Modulator NGSS

SKU #LGT-350
Availability: In Stock
Plug the flashlight transmitter into a cell phone, play a song, and the sound will "ride" the light beam to the solar panel receiver!


This has to be one of the most engaging light modulation demos ever! The Light Modulator is an easy-to-use, plug-and-play demonstrator of light and physics principles that will leave your students in awe. Plug the flashlight transmitter into a cell phone, play a song, and the sound will "ride" the light beam to the solar panel receiver! Ten unique experiments are provided. You'll be teaching concepts such as amplitude modulation, AC vs DC, fiber optics communication, persistence of vision, molecular kinetic theory, light properties, the Inverse Square Law and more. Requires 3 AAA and 2 AA batteries and a cell phone or MP3 player.

Here's how it works:

  1. Plug the flashlight into your mobile phone
  2. Activate the solar panel connected to a pre-amp and speaker
  3. Play a song on the phone and the sound will ride the light beam to the solar panel. How cool is that?

The phenomenon is known as Amplitude Modulation (AM), the same as the AM on your radio! You now have the ability to transmit sound (information) on a carrier (light) beam! We have fine-tuned and re-designed this technology into this easy-to-do kit for all science teachers and science demonstrators. All you need is your mobile phone and you're ready to amaze...

Kit includes:

  • 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 sheets


Lesson Ideas

10 Demos for your classroom

1. Transmit sound from your phone on a light beam

Connect the phone earphone socket to the flashlight and turn the volume up. Shine the flashlight beam on the solar panel. Block the beam with your hand. Prepare to be amazed!

2. Demonstrate the difference between AC and DC

Point the solar panel at a AC light source and the humming sound will indicate the changing electrical cycle.  Shine a flashlight beam onto the panel and there will be no humming sound. Cut the beam with your fingers to get a clicking-switching sound or try a laser pointer with the same outcome. Interestingly, this may be the first time many people hear the fingerprint switching sound of alternating (AC) and direct current (DC).  Of course, many know the rock band, AC/DC.

3. Listen to different light sources

Most electronic screens and monitors are refreshed at a high rate.  Investigate the invisible frequency by walking around the school / house and pointing the modulator solar panel at different types of screens, eg. a computer monitor, cell phone screen, TV screen.  You will hear a wide range of frequencies.  Also try the remote controls of the TV and any novelty light-up source, such as the bulb shaped LED light included in the kit.



4. Make a photophone: Place your voice on a light beam

When you talk into the tube, the sound pressure waves travel down the tube causing the elastic film to vibrate. The light hitting the mirror would normally reflect off at one angle but now because of the vibrations, the light is scattered at various angles.  This will vary the light intensity reaching the solar panel, so the voice vibrations are converted to variable electrical signals!

5. Show that an increase in sound volume causes an increase in kinetic energy

Most students are familiar with the vibrations produced by the open cone of a speaker. For this demo you will need to position the modulator receiver so the speaker faces up.  
Add a number of the small beads supplied, to the speaker cone and cover with the acrylic bottle.  Turn the system on, play a song at low volume and gradually increase the volume.  Note how the beads’ random movement increase with an increase in sound energy.

6. Model molecular phase changes

Explain to the students that you will use sound energy to model heat energy to visualise a change in state, eg the melting of ice or the evaporation of water. Activate the included RGB strobe ring and gradually bring it closer to the solar panel. (The ball contains a red, green & blue LED that flickers at a fast rate). You should hear an increasing humming sound. Point out that the increasing kinetic energy of the speaker is transferred to the particles which is equivalent to heat transferred from a hot plate. The higher the kinetic energy (heat), the faster the molecules move and some of the “molecules” may even gain sufficient energy to escape the liquid and enter the gas phase.

7. Produce a Laser show

Position the speaker so it faces up. Place the included round mirror on the speaker cone.  Do not stick the mirror to the speaker.  Clamp the laser pointer in a retort stand so the beam stays on and is stable with no vibration. Reflect the laser beam off the mirror onto the ceiling or a white board.  Activate the modulator and select a song with a lively beat.  Darken the room, turn up the audio input volume and hold the flashlight close to enjoy the modulated laser show.  [Laser not included]


8. Demonstrate the Inverse Square Law using sound

The Inverse Square Law states that the intensity of light decreases as the inverse square of distance (1/r2) This means that the light intensity at 1m from the source will decrease to ¼ at 2m and 1/9 at 3m from the source. Can you prove this in a qualitative way?  It is important that the students realise that the sound volume is proportional to the amount of light that strikes the solar panel.  Activate the modulator and play a song.  Start with the flashlight 1m from the solar panel and move back 1m and then another meter while observing the volume changes (which is proportional to intensity).  

9. Demonstrate modern fibre optic communication systems

For this demonstration you will need a cheap fibre optic bundle from a gift shop. These are often available as part of a table light display with a colour changing LED base.  Activate the modulator and project the light beam into the fibre optic bundle.  Bend the fibre optic bundle to demonstrate internal reflection and point at the solar panel.  Modern communication systems use modulated signals carried by light beams in clear fibre optic cables. This forms the basis of the new LiFi technology and the NBN (National Broadband Network in Australia).  [Optical fibre bundle not included].

10. Demonstrate Persistence of Vision

You may use any novelty light that uses fast flickering LEDs.  A few useful ones are the strobing RGB ring (included),  a rotating fan with LEDs and the light writer fan. Activate the modulator receiver & dim the lights.  
1. Ring:  Hold the fast flickering ring in front of the solar panel to hear the quick switching of the LEDs.  Then move the strobing ring in circles so the images gets spread out on the retina.  Now you can clearly see the flickering red, green & blue LEDs.      
2. Fan: Hold the lit up fan’s blade stationary in front of the solar panel to hear the fast switching LEDs.  Then let the blade freely rotate to see the ‘merged’ persistence of vision effect.  This is exactly what happens when you visit the cinema.

Write a Review


4 reviews
Perfect for Amazing Students
Review star icon Review star icon Review star icon Review star icon Review star icon Feb 11, 2019
This demo is mind-boggling! When every I show it to students, they are awe-struck, thinking that this is some magic trick. A very nice set of activities to teach students about waves, light, optics, etc. The flashing LED came broken, but I called and was able to get it replaced for free.
Jeromy Rech

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unique sound demo
Review star icon Review star icon Review star icon Review star icon Review star icon Feb 11, 2019
I have two audience members come up to help hold everything and used a microphone on a mic stand so the audience in the lunch room could hear the sound effects and the music when I used my MP3 with the modulator. The package comes with many different props to do a variety of demonstrations. The only other thing extra I bought was some fiber optic strands. This item was a perfect addition to my science of sound presentation. Very unique and cool.
mark carter

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100% Awesome
Review star icon Review star icon Review star icon Review star icon Review star icon Sep 22, 2018
Even the adults were amazed. An excellent way to explain AM, FM, cell phone transmissions and more. I'm using it in college classes and for young children with age appropriate explanations of the content. 100% WOW factor and clearly shows what you've been explaining.
Jaime Demick

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1   0

Something different
Review star icon Review star icon Review star icon Review star icon Review star icon Sep 6, 2018
This is a way cool demonstration and perfect to add to my sound and light presentation. I found a fiber optics bundle on line as shown in the video because it does not come with the kit. Great information page and the props seem to be well made. I recommend removing the batteries from the speaker box when storing and you have to charge the speaker itself with the enclosed cord but you supply the plug. I like the light!
mark carter

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This product will support your students' understanding of the Next Generation Science Standards (NGSS)*, as shown in the table below.

Suggested Science Idea(s)


Students can use the Light Modulator and the various accessories included in the kit to conduct a multitude of fascinating investigations. The different sources of light can be interpreted by the modulator into a variety of audible sounds.

Students can use the light modulator in a variety of investigations to better understand how light waves travel. The use of Fiber optics leads students to better understanding of real world technology.

Modern communication systems, such a long-distance phone lines and high-bandwidth communication line for computer, commonly use modulated signals carried on a beam of light. The relatively high frequency of visual light can carry a lot more information than lower frequency radio waves.


* NGSS is a registered trademark of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of, and do not endorse, this product.

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