Which device was developed by A G Bell to demonstrate the use of electronic wireless communication through visible light media?

Question

Prepp Team · Accepted Answer

Understanding Bell's Wireless Light Communication

The question asks about a specific device developed by the famous inventor Alexander Graham Bell. The device was designed to demonstrate electronic wireless communication, but specifically using visible light as the medium to carry the signal. Let's look at the options provided and determine which one fits this description.

Analyzing the Options

We are given four options:

Photo diode
Photo phone
Photo recorder
Smart phone

Let's consider each option in the context of Alexander Graham Bell's work and early wireless communication using light.

Photo diode: A photo diode is a semiconductor device that converts light into electrical current. While crucial for detecting light signals, it is a component, not a complete communication device developed by Bell for demonstrating wireless communication via light.
Photo phone: The Photo phone (sometimes called the Photophone) was indeed invented by Alexander Graham Bell and his assistant Charles Sumner Tainter. It used a beam of sunlight (or other light source) to transmit speech wirelessly. A diaphragm vibrated in response to sound waves, causing variations in the intensity of the reflected or transmitted light beam. At the receiving end, a selenium receiver converted the varying light intensity back into audible sound. This perfectly matches the description in the question: electronic wireless communication through visible light media.
Photo recorder: A "photo recorder" is not a commonly recognized historical communication device, especially not one associated with Alexander Graham Bell's work in wireless light communication. Recording sound or images via light involves different technologies.
Smart phone: A smart phone is a modern mobile electronic device that combines mobile phone and computing functions. It uses radio waves for wireless communication, not visible light for the primary communication medium, and is a 21st-century invention, far removed from Bell's era.

The Photo phone: Bell's Light-Based Communicator

Based on our analysis, the device developed by Alexander Graham Bell specifically for demonstrating electronic wireless communication using visible light was the Photo phone. Bell considered the Photo phone to be one of his most significant inventions.

The basic principle of the Photo phone involved modulating a beam of light with audio signals. Here’s a simplified breakdown:

Transmitter: Sound waves (like voice) would vibrate a mirror or diaphragm. This vibration would slightly change the path or intensity of a beam of light directed onto it (often sunlight).
Receiver: At the receiving end, a light-sensitive material (like selenium) would detect the varying light beam. Selenium's electrical resistance changes based on the amount of light hitting it.
Sound Reproduction: The changing resistance in the selenium would cause variations in an electrical current, which could then be converted back into sound using an earphone or speaker.

This system successfully transmitted speech over distances using light.

Conclusion

The device that fits the description of being developed by A. G. Bell for electronic wireless communication using visible light is the Photo phone.

Device	Inventor / Era	Communication Medium	Relevance to Question
Photo diode	Various, later than Bell	Electrical component (light detection)	Component, not Bell's device for this purpose.
Photo phone	Alexander Graham Bell	Visible light	Device developed by Bell for wireless light communication. Correct.
Photo recorder	Not a standard term	N/A	Not a known device by Bell for this purpose.
Smart phone	Modern era	Radio waves	Modern device, uses radio waves, not relevant.

Revision Table: Key Concepts

Concept	Explanation	Connection to Question
Alexander Graham Bell	Known for inventing the telephone and other communication devices.	The inventor mentioned in the question.
Wireless Communication	Transmitting information without physical wires.	The core concept explored by the device.
Visible Light Communication	Using light waves to carry data or signals.	The specific medium used by the Photo phone as described in the question.
Photo phone	A device invented by Bell that transmitted speech wirelessly using light.	The correct answer; the device that meets all criteria.

Additional Information on Photo phone History

The Photo phone was patented by Alexander Graham Bell in 1880. He conducted successful tests, transmitting speech over distances of several hundred meters using sunlight. Although it was an early form of wireless communication and a precursor to fiber optics and other light-based communication technologies, it didn't become commercially viable at the time due to practical challenges like the need for clear line-of-sight and the impact of weather conditions on the light beam.

Despite its lack of commercial success in its original form, the principle demonstrated by the Photo phone—using light for communication—was revolutionary and highlighted Bell's forward thinking beyond just wired telephony.