Students who demonstrate understanding can: Use mathematical representations to describe a simple model for waves that includes how the amplitude of a wave is related to the energy in a wave.
Clarification statement: Emphasis is on describing waves with both qualitative and quantitative thinking.
Assessment boundary: Assessment does not include electromagnetic waves and is limited to standard repeating waves.
Official wording from the Next Generation Science Standards (NGSS Lead States, 2013). NGSS is a registered trademark of WestEd. Neither WestEd nor the lead states and partners that developed the NGSS were involved in the production of this page, and they do not endorse it. View on nextgenscience.org
A wave is a repeating disturbance that carries energy from place to place without carrying the material along with it. Ripples move across a pond while the water itself mostly bobs up and down. Students describe simple repeating waves using a few measurable features: amplitude (how far the medium moves from rest), wavelength (the distance from one crest to the next) and frequency (how many waves pass a point each second).
The central idea is that amplitude is linked to energy. A gentle wave lapping at the shore and a towering storm wave can have the same wavelength, but the storm wave, with its far greater amplitude, carries much more energy and does much more damage. In sound, a larger amplitude means a louder sound. For a standard wave, doubling the amplitude gives about four times the energy.
Mathematical representations include labeled wave diagrams, tables and simple calculations such as finding wave speed from frequency and wavelength. Light and other electromagnetic waves are not part of this expectation.
A floating ball bobs up and down as a wave passes but stays in roughly the same place. The energy travels; the water mostly does not.
For mechanical waves in this unit, energy is tied to amplitude. Two waves with the same wavelength can carry very different energy.
Amplitude is measured from the rest position to a crest, which is half the trough to crest height.
Pitch depends on frequency, while loudness depends on amplitude. A quiet sound can be high pitched.
A rope wave has crests 2 m apart, rises 0.3 m above its rest position, and 3 waves pass a point every second. Find the amplitude, wavelength, frequency and speed. What happens to the energy if the amplitude doubles?
Answer: Amplitude 0.3 m, wavelength 2 m, frequency 3 Hz, speed 6 m/s; doubling the amplitude carries about 4 times the energy.
Use a long spring toy or a rope on the floor: students make waves with small and large shakes and feel the difference in effort. Then have them sketch the waves, label the features, and compare a table of wave measurements.
Assessment usually gives a wave diagram with a grid and asks for amplitude or wavelength, or compares two waves and asks which carries more energy. Make sure students measure amplitude from the center line.
Original questions written for this standard. Choose an option or type your answer, then press Check. Every question has a worked explanation.
Answer: C) Wave B
Greater amplitude means more energy, so wave B carries more.
Answer: 10 (also accepted: 10 m/s)
Speed = frequency × wavelength = 4 × 2.5 = 10 m/s.
Answer: A) 0.5 m
Amplitude is measured from the rest position to a crest, so it is 0.5 m.
Answer: D) It bobs up and down in about the same place
Waves transfer energy, not matter, so the duck mostly moves up and down.
Answer: amplitude
Larger amplitude sound waves carry more energy and sound louder.
Answer: B) four times as much
Wave energy depends on the square of amplitude, so doubling amplitude gives about 2 × 2 = 4 times the energy.
Develop a model of waves to describe patterns in terms of amplitude and wavelength and that waves can cause objects to move.
A full lesson with slides, activities and an exit ticket on wave amplitude and energy, pitched to grades 6-8 and editable in PowerPoint or Google Slides.
Make a lesson →A printable, differentiated worksheet on MS-PS4-1 with an answer key, ready in about a minute.
Make a worksheet →Turn wave amplitude and energy into a quiz students answer online that marks itself, with a class summary for you.
Build a test →No. The assessment boundary excludes electromagnetic waves and limits the work to standard repeating waves, such as water, rope and sound waves.
Reading amplitude and wavelength from diagrams, using frequency, and simple relationships such as speed = frequency × wavelength.