Fenna shakes the end of a rope, sending a steady wave train toward a post. Then she doubles her shaking rate.
The rope still sets the speed, so the crests travel no faster. But crests now leave her hand twice as often. What happens to the spacing between them?
Think about two neighboring crests.
The spacing between them is set by two things: how fast a crest travels away, and how soon the next crest is made.
Crest one leaves the hand and travels away at the rope's speed. Crest two is made one vibration later and follows it.
Shake twice as fast, and crest two is made in half the time. Crest one has traveled only half as far when crest two sets out, so the gap between them is half what it was.
The flip runs the same way. Shake more slowly, and each new crest sets out later, so the gaps stretch: the wavelength grows.
Nothing about the rope changed, so the speed never changed. Frequency and wavelength traded off against each other.
A dipper in a ripple tank is sped up so it bobs more times each second. The water is unchanged. What happens to the spacing of the ripple crests?
The water is unchanged, so the ripples' speed is unchanged.
Crests are now made more often, so each new crest sets out sooner, while the one ahead has traveled a shorter distance.
The spacing shrinks: the wavelength decreases.
A wave machine on a long cord is turned down to half its vibration rate. What happens to the wavelength of the waves on the cord?
The cord is unchanged, so the wave speed is unchanged.
Crests are now made half as often, so each crest travels twice as long before the next one sets out.
The wavelength grows: each gap stretches to twice what it was.
Hale shakes the end of a rope faster. The rope is unchanged. What happens to the wavelength of the waves?
Why does faster shaking crowd a rope's crests closer together?
Griet says: 'If I shake the end of a long spring more slowly, the waves on it get longer.' Is Griet correct?
A machine shaking one end of a clothesline is slowed down. The line is unchanged. What happens to the waves on the line?
A dipper bobbing in a ripple tank is sped up, and the ripple crests end up closer together. Why?
Eirik's rope is shaken at 2 Hz. Fenna shakes an identical rope at 6 Hz. Which statement compares the two wave trains?