Idea 2of 9Builds onThe pattern moves, the stuff stays
How tall
Shake the rope harder. What changes?
Today you'll discover
- what shaking harder changes, and what it leaves alone
- where a wave keeps its energy
- the name for a wave's height
Think firstA rope shaken gently, then shaken harder
You shake the rope harder, at the same rate. What changes in the picture?
Decide first, then press Next. Watch the height change while the spacing stays put.
A wave on a rope with a dashed middle line. After a prediction, the rope is redrawn shaken harder, with taller crests and deeper troughs at the same spacing, then a bracket is drawn from the middle line up to a crest and named. The last step asks how a brick's ripple differs from a pebble's.
See the whole ideathe big idea and the key word, in one place
The big idea
Amplitude is the height: midline to crest. More height, more energy.
Easy to get wrongA taller wave is not a faster wave. Shake the rope as hard as you like: each crest still travels at the rope's own speed.
Key word
- amplitude
- the greatest distance of the medium from its rest position, measured from the midline to a crest; the energy rides here
About this modelThe pattern travels; the particle only bobs. One square of the drawing is 0.5 m.
The pattern travels; the particle only bobs. One square of the drawing is 0.5 m.
Ready to use it?
- Read the amplitude off a drawn wave and say what shaking harder changes.