Laser Waves and Vinyl Grooves: A Perfectly Imperfect Diffraction
James Dauer
Award: Top 100
School: sleepy hollow high school
Teacher: leila madani
Category: Contrived
Photo #21089
Laser Waves and Vinyl Grooves: A Perfectly Imperfect Diffraction
Vinyl records aren't just a cultural revival, they demonstrate physics in action. The grooves etched into the record encode sound as tiny vertical variations. When the needle traces these grooves, it vibrates, converting mechanical energy into electrical signals that produce music.
In this photo, the grooves interact with light. When I directed a red laser onto the vinyl, the grooves acted as a diffraction grating. Due to their spacing, which is comparable to the wavelength of visible light, the light diffracts and interferes, creating a series of bright and dark spots. These result from constructive and destructive interference, respectively. The central maximum is the brightest because it represents the light waves closest to the source, while higher-order maxima become dimmer as the light spreads.
When I used both red and green lasers, which differ in wavelength, this difference causes the two colors to diffract at different angles. The red light, having a longer wavelength, produces broader diffraction patterns, while green light, with a shorter wavelength, creates tighter, more distinct patterns.
Just like the song on the vinyl, "It Isn't Perfect But It Might Be!" by Olivia Dean, embraces imperfection, the record's microscopic irregularities produce rich diffraction patterns and a vibrant display of light waves. What was designed to create mechanical sound waves also reveals the wave nature of electromagnetic light.
Connecting music and optics, this image turns sound grooves into a wonder of interference and diffraction, revealing deeper physics in everyday objects.
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