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Observatory

Unit 02 · Physics 1

Waves & Sound

What travels when nothing travels: pulses on a rope, standing patterns that never move, and the pitch a moving siren actually carries.

Work through them in order: each lesson assumes the one before it. Every lesson asks you to commit to a prediction, then lets you test it against a simulation of the real equations.

  1. 01

    Wave Pulses & Superposition

    A shape crosses the whole rope while the rope itself stays home, and two pulses pass straight through each other without a scratch.

    Topics: Wave speed on a string · Medium and wave · Reflection at a boundary · Superposition

    35 min4 checkpoints
  2. 02

    Standing Waves & Harmonics

    Two waves, opposite directions, one string, and a pattern that heaves in place even though nothing has stopped travelling.

    Topics: Standing waves · Harmonics on a string · Nodes and antinodes · Pipes

    35 min4 checkpoints
  3. 03

    Sound Waves & Beats

    Sound is a crowd of air being squeezed rather than a wiggle going up and down, and beats are what two steady tones do when they nearly agree.

    Topics: Longitudinal waves · Pressure and displacement · Speed of sound · Beats

    35 min4 checkpoints
  4. 04

    The Doppler Effect

    The siren never changes its note. The pitch you hear changes because each crest starts from a different place.

    Topics: Moving source · Moving observer · The Doppler formula · Shock waves

    35 min3 checkpoints