Grade 8 · Physics · Wave Investigations · Part 2

WaveLab 2

Use the PhET simulation to investigate wave properties. Click 🌊 PhET Window in the top bar to open the simulation — you can drag it, resize it, and keep it visible alongside this worksheet the whole time.

Amplitude Wavelength λ Period T & Frequency f Wave Speed v=fλ Frequency ↔ λ Relationship Amplitude ↔ Speed

🎥 50-Minute Teams Session Guide — Ahmad Ghozlan

0–15 min · Share your screen: Open this page. Click "🌊 PhET Window" → the sim opens as a floating window you can drag and resize. Show students how to: set Oscillate mode, set Tension to High, set Damping to None, enable Rulers and Timer. Do Investigation 1 (amplitude) together live. Share the link in Teams chat.

15–40 min · Students work independently: Students open the link on their own devices — sim and worksheet on the same page. You stay on Teams. Monitor chat. The answer key card below (yellow) is visible only on this page to help you guide students who are stuck.

40–50 min · Review together: Share screen again. Walk through answers — ask students to share their v=fλ calculations in the chat. Discuss the amplitude-speed discovery. Students submit before session ends.

🌊 PhET Simulation — Wave on a String

The simulation opens as a floating window you can drag to any position on your screen and resize. Keep it next to the worksheet so you never need to switch tabs.

💡 Tip for students: Drag the PhET window to the right side of your screen, and use the left side for the worksheet.

📋 How to Use the Simulation — Read Before Starting

▼

Select Oscillate at the top — this creates a continuous wave.

Set Tension to High — keep this for ALL investigations so results are consistent.

Set Damping to None — slider all the way left so the wave doesn't fade.

Select No End — the wave travels freely without reflecting.

Tick Rulers — a ruler appears. Drag it to measure wavelength (crest to crest).

Tick Timer — a stopwatch appears. Use it to time one full oscillation.

Press Pause ⏸ to freeze the wave — much easier to measure a still wave!

Frequency slider

Controls oscillations per second (Hz). Higher = more waves, shorter wavelength.

Amplitude slider

Controls wave height (cm). Does NOT affect speed — you will prove this!

Ruler tool

Drag to measure crest-to-crest distance = wavelength λ in cm.

Timer tool

Time one full up-down-up cycle of any dot = period T in seconds.

📋 Expected Values — Teacher Reference (Tension: High, No End)

f = 1.00 Hz → λ

≈ 6.2 cm

f = 1.50 Hz → λ

≈ 4.1 cm

f = 2.00 Hz → λ

≈ 3.1 cm

f = 3.00 Hz → λ

≈ 2.0 cm

T at f=1.50 Hz

≈ 0.67 s

Wave speed v = fλ

≈ 6.0–6.5 cm/s

Amplitude effect on v

None — v constant

f ↔ λ relationship

Inverse (fλ = const)

🔬 Wave Investigations 0 / 5 completed

Measuring Amplitude

Observe what amplitude is and how it affects the wave

Not started

▼

Setup

In the PhET sim: Oscillate · Tension: High · Damping: None · No End. Set Frequency = 1.50 Hz. Enable Rulers. Wait 3 seconds for the wave to develop. Then ⏸ Pause.

Measure

Use the ruler to measure the amplitude — the height from the flat centre line (equilibrium) up to the highest point (crest). Try three different amplitude settings and record the wavelength each time.

Amplitude set (cm)

cm — read from slider

Measured height (cm)

cm — use ruler

Wavelength at this amplitude (cm)

cm — should stay ~4.1 cm

What does amplitude represent?

Measuring Wavelength (λ)

Use the ruler to measure crest-to-crest distance precisely

Not started

▼

Setup & Measure

Set Frequency = 1.50 Hz, Amplitude = 0.75 cm, Tension High, Damping None. Let the wave develop, then ⏸ Pause. Drag the ruler to measure from one crest to the next crest. This is wavelength λ.

Frequency (Hz)

set on slider

Wavelength λ (cm)

cm — pause sim & use ruler

Define wavelength in your own words

Period (T) and Frequency (f = 1/T)

Time one full oscillation and verify f = 1/T

Not started

▼

Measure Period T

Keep f = 1.50 Hz. Enable the Timer in the sim. Unpause. Watch the green dot at the source go up, reach the top, come back down, go to the bottom, and return to centre — that is one complete oscillation. Start and stop the timer for exactly one cycle. This time is period T.

Period T measured (s)

seconds — one full cycle

Calculated f = 1/T

Enter T above

Hz — should match slider

Frequency on slider (Hz)

Hz — read from sim

Relationship between T and f

Wave Speed: v = f × λ

Calculate wave speed and prove it stays constant

Not started

▼

Calculate Speed at f = 1.50 Hz

Use your values from Investigations 2 and 3. Calculate v = f × λ. Keep λ in cm and f in Hz — your speed will be in cm/s.

f (Hz)

λ (cm)

v = f × λ (cm/s)

—

Now change frequency to 3.00 Hz and repeat

Change frequency to 3.00 Hz. Pause and measure the new wavelength λ. Calculate the new speed. Does the speed change?

f (Hz)

λ (cm)

v = f × λ (cm/s)

—

What did you discover about wave speed?

Frequency ↔ Wavelength Relationship

Discover the inverse relationship using a data table

Not started

▼

Data Collection — 4 different frequencies

Set each frequency below, let the wave develop, pause, measure λ. Keep Tension High and Damping None throughout.

Trial	Frequency f (Hz)	Wavelength λ (cm)	Speed v=fλ (cm/s)
1			—
2			—
3			—
4			—

The relationship between frequency and wavelength

★

Bonus — Does Amplitude Affect Wave Speed?

Test a common misconception — challenge your intuition!

Optional

▼

Predict first, then test

Set f = 1.50 Hz. Try three amplitude values: 0.25 cm, 0.75 cm, and 1.25 cm. For each, pause and measure λ, then calculate v = fλ.

Amplitude 0.25 cm → λ (cm)

Amplitude 0.75 cm → λ (cm)

Amplitude 1.25 cm → λ (cm)

Speeds compared

Enter λ values above

AI Tutor — Was your prediction correct?

📊 Submit Your Investigation Results

Full Name *

Class *

0 / 5 investigations completed

⚡

—

Your Score

Ahmad reviews your wave speed calculations and conclusions in the next class.