Physics — Algebra and Trigonometry · 40 minutes
Suggested grades 11–12 · Unit 2: Energy and Waves · Lesson 2 of 2
Read Frequency, Wavelength and Speed Together
Use wave relationships while avoiding the claim that a source’s frequency must change whenever the medium changes.
Mr. S Teaches · Original starter lesson · HS-PHYS-04 · Grade range is planning guidance.Watch, notice, discuss
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Wave Equation | Waves | Physics | FuseSchool
By FuseSchool - Global Education
Use v = fλ to check the lesson’s calculations and predict which quantity changes under a specified condition.
Open on YouTube: Wave Equation | Waves | Physics | FuseSchool (opens a new tab) ↗Transverse & Longitudinal Waves | Waves | Physics | FuseSchool
By FuseSchool - Global Education
Identify wavelength and particle motion in two wave models; use as conceptual support before numerical wave-speed work.
Open on YouTube: Transverse & Longitudinal Waves | Waves | Physics | FuseSchool (opens a new tab) ↗What idea from the video helps you calculate wavelength and predict how one changed condition affects a wave model? Identify one useful example and one limit of the video's model or explanation.
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Learning objective
Calculate wavelength and predict how one changed condition affects a wave model.
Before you begin
- Rearrange v=fλ and read units.
Gather your materials
- Paper or notebook
- Pencil; calculator optional for numerical work; all task data supplied below
Language to know
- frequency
- Number of cycles per second.
- wavelength
- Distance between corresponding points on successive cycles.
- wave speed
- Rate at which the modeled wave pattern travels through a medium.
Understand the concept
Technical briefing: A source produces a 170 Hz sound wave traveling at 340 m/s in a stated medium, so λ=v/f. If a source’s frequency is maintained while transmission enters a medium with a different wave speed, wavelength can change. Frequency is not the same quantity as loudness. The values are stipulated model data; temperature, medium properties and transmission details are omitted. Use diagrams and calculations only, without loud sounds or hearing tests.
Teach it step by step
- Read the briefing and write the quantity and unit associated with each symbol.
- Calculate the first wavelength and draw two labeled cycles to scale on a schematic.
- Keep frequency fixed and recalculate wavelength for a stated speed of 510 m/s.
- Explain in words which quantities changed and cite the condition that allowed frequency to stay fixed.
Make the thinking visible
Worked example or model response
At 340 m/s, λ=340/170=2 m. At 510 m/s with the same 170 Hz source, λ=3 m. Drawing more closely packed cycles for the faster case would contradict these given values.
Guided practice
Together calculate the frequency of a model wave with speed 12 m/s and wavelength 0.5 m.
Independent practice
For a wave traveling at 300 m/s, compare wavelengths at 100 Hz and 150 Hz. Write an explanation distinguishing increased frequency from increased amplitude.
Quick assessment
If frequency doubles while wave speed stays fixed, what happens to wavelength?
Answer key & assessment criteria
Answers and teaching guidance
- Guided: f=12/0.5=24 Hz.
- Independent: Wavelengths are 3 m and 2 m respectively. Frequency counts cycles per second; amplitude describes displacement or another wave-strength measure in the model.
- Quick check: Wavelength halves, since v=fλ remains fixed under the stated condition.
Look for: Assess the stated objective using the concrete criteria and explanations in the answer key. Invite an alternative supported solution; distinguish a model’s prediction from an established observation.
Make it work for your learner
More support
Provide a quantity–symbol–unit table and use silent line diagrams for every task.
Extension challenge
Compare two media using the same frequency and explain why a measured wavelength could help infer wave speed.
Verified references · Selected contributions
Standards connections
Selected NGSS high school-band contribution; full performance requires additional evidence and instruction.
Subject-content standards
These records identify the part of a subject standard practiced here. Course placement is instructional guidance; the source’s category or band remains authoritative.
Contributes to NGSS performance expectation
HS-PS4-1
NGSS · High school band
Relate wave frequency, wavelength and speed mathematically.
Read the official performance expectation ↗Selected algebraic relationships describe stipulated wave data. The activity does not test multiple media empirically or establish all wave propagation mechanisms.
Verified 2026-11-04. Selected contribution, not full attainment.
Supporting literacy connections
These records apply to the specified reading, writing or communication task. They do not establish subject-content alignment.
Supporting Common Core literacy connection
RST.11-12.1
Common Core · Grades 11–12
Analyze technical details, distinctions and gaps using textual evidence.
Read the official standard ↗The activity explicitly analyzes the provided technical text, table or model. It contributes selected literacy practice rather than complete grade-band reading coverage or independent subject-content alignment.
Verified 2026-11-04. Selected contribution, not full attainment.