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Concept module

Wave Speed and Wavelength

Follow one traveling wave across the same medium and connect crest spacing, travel delay, source timing, and the relation v = f lambda on one honest live stage.

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Starter track

Step 2 of 90 / 9 complete

Waves

Earlier steps still set up Wave Speed and Wavelength.

1. Simple Harmonic Motion2. Wave Speed and Wavelength3. Sound Waves and Longitudinal Motion4. Pitch, Frequency, and Loudness / Intensity+5 more steps

Previous step: Simple Harmonic Motion.

Start from track beginning

Why it behaves this way

Explanation

A traveling wave ties together two kinds of spacing at once. Along the medium, lambda tells you how far it is from one crest to the next. At one point in the medium, the period tells you how long it takes for that pattern to repeat in time.

This lab keeps one source, one moving wave train, and one probe on the same compact stage so the relation v = f lambda stays honest. If a crest train moves faster through the medium, or if the crests are packed differently, the source timing and probe delay must change with it.

Key ideas

01Wave speed tells you how quickly one phase point such as a crest moves through the medium, while wavelength tells you how far apart repeating spatial features are.

02Frequency and period describe the time behavior at one location. For the same traveling wave, f = v / lambda and T = 1 / f = lambda / v.

03Moving the probe does not change the wave itself. It only changes how much travel delay and phase lag separate that point from the source.

Frozen walkthrough

Step through the frozen example

Frozen walkthrough

These examples read the current wave speed, wavelength, and probe position from the same live stage, so the algebra stays tied to the crest train you are actually watching.

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Frozen valuesUsing frozen parameters

For the current traveling wave with v = 2.4\,\mathrm{m/s} and lambda = 1.6\,\mathrm{m}, what frequency and period must the source have?

v

Wave speed

2.4 m/s

λ

Wavelength

1.6 m

f

Frequency

1.5 Hz

T

Period

0.67 s

1. Start from the wave relation

Use

v = f λ

, so

f = \frac{v}{λ}

, and then

T = \frac{1}{f}

2. Substitute the live values

f = \frac{2}{.} 41.6 = 1.5 Hz

3. Convert to a time period

That gives

T = \frac{1}{f} = 0.67 s

, so one full source cycle launches one more wavelength every 0.67 seconds.

Current timing

f = 1.5 Hz, T = 0.67 s

The wave cycles more slowly here, so each point waits longer for the next full oscillation and the period stays noticeably longer.

Common misconception

A faster wave must always have a higher frequency because it is moving more quickly.

Wave speed and frequency are not the same idea. Speed is how fast the pattern travels through the medium, while frequency is how often one point oscillates.

If the speed changes while the crest spacing stays fixed, the frequency changes. If the speed changes while the source frequency is fixed instead, the wavelength changes. The relation keeps all four quantities consistent.

Mini challenge

You are not allowed to move the probe, and the wave speed stays fixed. What one change makes the source oscillate more slowly while the crest train still reaches the same point?

Make a prediction before you reveal the next step.

Decide whether you should increase amplitude, increase wavelength, or slide the probe farther right.

Check your reasoning against the live bench.

Increase the wavelength.

With v fixed, the frequency is f = v / lambda. A larger wavelength means fewer cycles fit into each meter, so the source frequency drops and the period gets longer.

Quick test

Variable effect

Question 1 of 4

Use the live wave relation, not memory alone. These checks are about how spacing, timing, and downstream delay fit together.

The wave speed stays fixed, but lambda doubles. What happens to f and T?

Use the live bench to test the result before moving on.

Accessibility

The simulation shows one source on the left launching a transverse traveling wave across a horizontal medium. A movable probe marks one downstream position on the wave, and optional overlays can label one wavelength, the source-to-probe delay, and the distance a crest covers in one period.

A readout card summarizes the current wave speed, wavelength, frequency, period, probe position, and probe displacement so the key relation stays visible without leaving the stage.

Graph summary

The displacement graph compares source motion with probe motion on the same time axis, so the user can read delay and phase differences honestly. The phase-map graph shows how many cycles of lag accumulate with downstream distance, and hovering that graph moves the live probe to the matching position.

Keep this idea moving

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