A Voice on a Beam of Light
Most people know Alexander Graham Bell as the inventor of the telephone, a device that carried human speech through electrical wires. Yet Bell himself considered another creation to be his greatest achievement. In the spring of 1880, working alongside his assistant Charles Sumner Tainter, Bell built a remarkable machine called the photophone. Instead of relying on copper cables to send speech from one place to another, the photophone did something that seemed like magic: it transmitted the human voice along a shimmering beam of sunlight.
To understand how the photophone worked, it helps to look at the science of sound and light. Sound travels in invisible waves of vibrating air. When you speak, your vocal cords push air molecules back and forth, creating these ripples. Bell and Tainter wondered if they could capture those sound ripples and transfer them onto light waves. To test this idea, they designed a special transmitter equipped with a very thin, flexible mirror. When a person spoke into the mouthpiece of the transmitter, their vocal vibrations struck the back of the mirror, causing the delicate glass to vibrate and bend slightly.
- transmitted:
- Sent or passed along from one person, place, or thing to another.
- flexible:
- Capable of bending easily without breaking.
- modulated:
- Changed or varied the rhythm, intensity, or pattern of something such as a wave.
- resistance:
- A measure of how much an object or material opposes the flow of electric current.
- diaphragm:
- A thin, flexible sheet or disk that vibrates to create or receive sound waves.
- obstacles:
- Things that stand in the way or block progress.
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Preview questions from this passageShowHide
- 1What invention did Alexander Graham Bell consider his greatest achievement?
- 2How does human speech create sound waves according to the text?
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About this explanatory article passage for 5th Grade
“A Voice on a Beam of Light” is a explanatory article reading passage about Alexander Graham Bell's Photophone, written for 5th Grade. It takes about 4 minutes to read (531 words) and comes with an interactive quiz and a printable worksheet with comprehension questions and an answer key.