Particles don´t spread out, pass through each other, add or cancel... but waves do.
What quantities do we use to model waves? Sound and light are very different but are modelled in the same way.
Key Concepts
When a ball hits the surface of a pond, it gives energy to the surface. This energy spreads out. All waves involve the transfer of energy.
Use quizzes to practise application of theory.
START QUIZ!
Which of the following would not produce circular wavefronts?
Circular wavefronts come from point sources, a storm is not a point. A bee and stone are not points either but are closer approximations than a storm
A wave propagates as if made of a series of point sources. Which of the following diagrams represents the wavefront formed by the line of points?
A line of small balls joined by elastic strings lying on a frictionless table is disturbed in a horizontal direction as shown.
Which forms of energy does the string of balls get from the wave pulse?
The balls move and the strings are stretched
There is no gravitational PE since the disturbance is horizontal.
A horizontal wave pulse reflects off a fixed end as shown
What forms of energy are passed on to the clamp
The reflected wave is the same as the incident wave just inverted.
If the wave was not horizontal it would be difficult to explain where the gravitational PE has gone
When a sound wave propagates through a gas, what form of energy do the gas atoms receive?
There are no forces between gas atoms so no elastic PE.
atoms could be lifted but let´s ignore that and anyway KE + gravitational isn´t an option
The diagram represents the position of a series of balls connected with elastic string as a vertical pulse passes.
The green ball has
At max displacement the velocity = 0
The elastic string has elastic PE not the ball
The ball is lifted so has gravitational PE
Which diagram is correctly labeled?
λ wavelength
A Amplitude
Wavelength is distance between peaks
amplitude is max displacement from the equilibrium position
A wave in a string travels at 5ms-1 and has a wavelength of 2m
The frequency of the wave is:
f = v/λ = 5/2
How much of Introduction to waves have you understood?
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