Explicit physics instruction
Use v=fλ. Units must be consistent: Hz is s⁻¹, wavelength in metres gives speed in m/s.
A wave with f=5 Hz and λ=2 m travels at v=10 m/s. If the same medium keeps v fixed and f doubles, λ must halve.
Changing source frequency does not automatically change wave speed in the same medium.
Core relation: v=fλ.
Worked example
A wave with f=5 Hz and λ=2 m travels at v=10 m/s. If the same medium keeps v fixed and f doubles, λ must halve.
Guided question
A wave travels 12 m/s at 3 Hz. Find wavelength.
Independent work
- Solve three wave-speed or wavelength questions.
- Sketch one interference case.
- State one medium/source assumption.
Misconception check
Matter in the medium does not generally travel with the wave over long distances; the disturbance and energy propagate.
Formative check
If speed is constant and frequency doubles, what happens to wavelength?
Reveal response
It halves.
Mentor evidence conference
Ask Archaemenes to audit units, medium assumptions, and superposition reasoning.
Teacher guidance
Foundation: Calculate with v=fλ.
Core: Interpret interference and standing-wave diagrams.
Extended: Evaluate residuals and boundary-condition effects.