HS-PS4-1: Frequency, Wavelength and Wave Speed
Also called NGSS HS-PS4-1 · Topic: Waves and Electromagnetic Radiation · Physical Science
The Official Wording
Use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling in various media.
Clarification statement: Examples of data could include electromagnetic radiation traveling in a vacuum and glass, sound waves traveling through air and water, and seismic waves traveling through the Earth.
Assessment boundary: Assessment is limited to algebraic relationships and describing those relationships qualitatively.
NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026
What HS-PS4-1 Means in Plain English
Students use the wave equation, speed equals frequency times wavelength, to argue how waves behave in different materials. Sound moves faster in water than in air, light slows down in glass, and seismic waves change speed as they pass through Earth's layers.
The math stays algebraic, and students also explain the relationships in words, such as why frequency stays fixed when a wave enters a new material. This builds on MS-PS4-1 and supports the wave and particle evidence in HS-PS4-3.
HS-PS4-1 I Can Statements
- I can use v = fλ to find a wave's speed.
- I can explain why frequency stays the same in a new material.
- I can predict how wavelength changes when wave speed changes.
HS-PS4-1 Worked Example
One tuning fork heard in two materials, worked with the wave equation.
A 440 Hz tuning fork rings in air, where sound travels at about 343 m/s, and then under water, where sound travels at about 1,480 m/s. Find the wavelength in each.
- Start from v = fλ and solve for wavelength.λ = v ÷ f
- Put in the speed of sound in air.λ = 343 ÷ 440 ≈ 0.78 m
- Under water the fork still vibrates 440 times a second, so the frequency stays 440 Hz.λ = 1,480 ÷ 440 ≈ 3.36 m
- Compare the two wavelengths with the two speeds.Both ratios ≈ 4.3
Check it: Multiply back: 440 × 0.78 ≈ 343 and 440 × 3.36 ≈ 1,478, which match the speeds we started with.
Common Mistakes with HS-PS4-1
Thinking frequency changes in a new material
“Sound speeds up in water, so its pitch goes up.”
Try this: The source sets the frequency, so it stays the same. When speed changes, the wavelength changes to match.
Dividing the wrong way
λ = f ÷ v, giving 1.28 for sound in air
Try this: Check units: m/s divided by 1/s leaves meters. Frequency divided by speed gives the wrong units, a sign the setup is flipped.
Thinking sound is fastest in air
“Air is thinner, so sound must travel faster there.”
Try this: Sound travels faster in water and solids because their particles are tightly linked. Light is the opposite, fastest in a vacuum.
Where HS-PS4-1 Fits
Practice HS-PS4-1
Quick Check
- A wave has a frequency of 5 Hz and a wavelength of 2 m. What is its speed?
- Light goes from air into glass and slows down. What happens to its wavelength?
- Two sounds travel through the same air, one at 200 Hz and one at 400 Hz. Which has the longer wavelength?