Mistake Master
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CED objectives

Properties of Wave Pulses and Waves

▶︎  Watch it animatedinteractive step-through · ~3 min · optional ⚙︎  Open the appletPulse Bench · run a pulse the length of the rope and read the tagged particle's trail against the distance the pulse covered

A wave transports energy between two locations while the medium stays put: each particle oscillates about its own equilibrium position and goes nowhere, so the cork bobs in place and the air molecule near a speaker moves back and forth about a fixed spot. A wave is transverse or longitudinal according to the direction a single particle moves relative to the direction of travel, which makes sound longitudinal however it is drawn. The speed of a mechanical wave is fixed by the medium, $v = \sqrt{F_T/(m/L)}$ on a string, so nothing the source does can change it.

Three errors dominate. Picturing the medium itself travelling with the wave, so air drifts across the room toward a listener. Calling a wave transverse because the drawing looks like a sine curve, without asking what the vertical axis plots or which way the particles actually move. And treating the wave speed as something the source controls, so shaking a rope harder or shouting louder is expected to speed the wave up, when those change the amplitude and the frequency and leave $v$ alone.

the shape moved right; the marked particle only moved up and down t t + Δt this particle moved DOWN, not right the pattern travels this way a cork bobs in place; the air near a speaker oscillates about a fixed spot. Energy moves, matter stays
Two snapshots of the same rope. The pattern has advanced and the marked particle has only gone up and down.
classify from the particle motion, never from the shape of the plot travel TRANSVERSE: particle across travel rope, water surface, light travel LONGITUDINAL: particle ALONG travel sound, however smoothly it gets drawn as a sine curve
The yellow arrows are the classification. A sound graph's vertical axis plots pressure, which is not a direction anything moves in.

The work

3 ways in · any order
Lesson
Properties of Wave Pulses and Waves

Keeps the medium oscillating in place while the energy travels, classifies a wave from the motion of one particle rather than the shape of the graph, and hands the wave speed to the medium rather than the source.

Skill check · 10 scenarios
Diagnostic
10-item topic check

Ten items spanning the failure modes of this topic: carrying the medium along with the wave, reading transverse off a sine-shaped drawing, and letting a louder or faster source speed the wave up. Take it cold to find which one is yours, or after the lesson to confirm it is not.

Not started · 10 items · ~15 min
Targeted Practice
Drill a single misconception

Pick one of the failure modes you missed and drill it on its own. The round is adaptive: two correct in a row clears it for now and moves you to the next. Two in a row is a checkpoint, not proof: if the error resurfaces later, the misconception comes back.

Take the diagnostic to identify your misconceptions