Physics / Lesson 04
Waves and information
Understand waves as propagating patterns that carry energy and information.
orient
Why this idea had to exist
Sound, light, water ripples, and signals look different, yet share a mathematical structure: local oscillation produces a pattern that propagates through space or a field.
intuition
Build a picture you can reason with
A stadium wave travels around an arena although each person only moves locally. The pattern has a speed distinct from the motion of its participants. When patterns overlap, their displacements add before continuing onward.
formalize
Give the intuition a precise edge
For a periodic wave, v=fλ. Phase specifies position within a cycle. In a linear medium, superposition adds simultaneous displacements, producing constructive or destructive interference without permanently consuming either wave.
work through
Follow the decisions, not just the symbols
A 440 Hz sound travels at 343 m/s, so λ=v/f≈0.78 m. Doubling frequency in the same medium halves wavelength because the propagation speed is set primarily by the medium.
experiment
Change one thing and watch the model answer
Combine two sinusoidal waves. Adjust frequency and phase, then identify beats, standing patterns, and points of destructive interference from the actual summed displacement.
retrieve
Close the page and reconstruct it
Answer before opening the explanation. Retrieval is evidence only when the answer is produced without a hint.
What changes when wave frequency doubles but speed stays fixed?
The wavelength halves so that the product of frequency and wavelength remains the same speed.
transfer
Move the idea into a new setting
Explain how noise-cancelling headphones can reduce a periodic sound without claiming that either sound wave ceases to exist everywhere.
reflect
Leave with a diagnostic habit
Track the oscillating quantity, the propagation medium or field, and the distinction between particle motion and pattern motion.
Source record
Follow the idea back.
- Reference
- University Physics
- Publisher
- OpenStax
- License
- CC BY 4.0
- Accessed
- 2026-08-12
- URL
- https://openstax.org/details/books/university-physics-volume-1