Can you come up with a more innovative way to transfer sound using a photophone?

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In summary, the conversation was about a design contest for a photophone challenge. The participants had to design an apparatus that could transfer an audible vocal message over a distance of at least 20m using visible light. The group in the conversation used a magnet attached to a diaphragm and an array of LEDs for the transmission end, while the receiving end used a traditional selenium solution. The conversation also discussed different ideas for the photophone, including using a photocell or a vibrating mirror, but ultimately the group ended up using an array of photo-resistors. One participant suggested using cellophane and smoke for encoding the voice in light, which was considered an original idea.
  • #1
freemind
[SOLVED] The photophone challenge

Hi everybody, (reply: "Hi, Dr. Nick" even though my name is not Nick)

I saw this design contest near where I live where participants had to design and build an apparatus that would transfer an audible vocal message over a distance of @ least 20m, by using visbile light. Of course, I'm talking about a photophone. Now, my group (me and 3 others) attached a magnet to a diaphragm that would vibrate in accordance with the sound, and since the moving magnet was in a solenoid, it would generate a current. This current would power an array of LEDs. As for the receiving end, we used the traditional selenium solution. Why so convoluted? For one thing, we weren't allowed to use transistors. Only the basic electrical components.
I would really like to hear how other people would have approached this. After all, this is not very original, and originality was stressed for the contest (which would explain why we didn't win the grand prize). How would you have done it?
 
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  • #2
What about using a photocell for receiving? Would this violate the rules?
 
  • #3
For the transmission end, I would have used a diaphram vibrating a light-weight mirror reflecting a bright light shone by a car headlamp.
 
  • #4
Actually, we did consider using a vibrating mirror, but quickly shot down the idea - too quickly i must say - since this was essentially how Bell did his photophone. We thought it wouldn't take us far in terms of originality, and sure enough, there were at least three groups that used the vibrating mirror, only one of them making it to the top 5.
We also considered a photcell initially, but soon realized that its generated current was too feeble to power the speaker without massive amplification. So we ended up using an array of photo-resistors. That way, our speaker was reliant upon the significant variations in current.
 
  • #5
Well, if originality is stressed I guess the problem is therefore very tricky (I did not know Bell had made a photophone - or maybe I forgot). How about a pair of cellophane or Saran Wrap squares suspended vertically ~1mm apart from each other and the gap in-between filled with smoke? Speaking into the cellophane vibrates it and therefore changes the distance-between layers and further-therefore the smoke thickness which finally affects the total opaqueness in real-time according to vocal-wave modulation. Shine a light through it while speaking and you have your voice encoded in light.
 
  • #6
Wow, that's an amazing idea! Although, I'm not sure if the fluctuations in pressure/density of the smoke will be significant enough to create marked variations in the amplitude/frequency of the light (perhaps I'm worrying too much ). Nevertheless, it is definitely quite original! :biggrin:
 

1. What is "The photophone challenge"?

The photophone challenge is a scientific experiment that tests the ability of light to transmit sound waves. It was first invented by Alexander Graham Bell in 1880 and is considered one of the earliest forms of wireless communication.

2. How does the photophone work?

The photophone works by using a beam of light to transmit sound waves. The sound waves cause vibrations in the mirror of the device, which in turn, modulate the light beam. The light beam is then received by a photodetector and converted back into sound waves, allowing for communication between two distant points.

3. What materials are needed for the photophone challenge?

The materials needed for the photophone challenge include a light source, a mirror, a photodetector, and a receiver for the sound waves. The light source can be a simple flashlight or a more powerful laser, while the mirror should be able to vibrate easily. The photodetector can be a solar cell or a photoresistor, and the receiver can be a speaker or headphones.

4. What is the significance of the photophone challenge?

The photophone challenge is significant because it demonstrates the potential of light as a medium for wireless communication. It paved the way for modern technologies such as fiber optics and laser communication. It also showcases the ingenuity and creativity of early scientists like Alexander Graham Bell.

5. Can anyone participate in the photophone challenge?

Yes, anyone can participate in the photophone challenge. It is a fun and educational experiment that can be done with basic materials. It is especially popular among science enthusiasts, students, and those interested in the history of communication technology.

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