In this topic we look at:
- oscillations of bodies that move back and forth periodically
- progressive waves that transfer energy and information through space
- the interference effects of these progressive waves, and other phenomena
- standing waves, where waves combine to become stationary (and therefore transferring no energy at all)
You will learn about simple harmonic motion, dispersion and guitar string frequencies, and be able to answer the following questions:
- How does a force that is proportional to displacement result in an oscillation?
- Are all oscillations simple harmonic?
- What is the connection between oscillations and waves?
- Are waves really made of an infinite number of wavelets?
Another physics book classic, the mass hanging on a spring. A bit easier to analyse than a pendulum but not as easy as the mass on a spring in space. Quite obvious that the acceleration is proportional to displacement, once you realise that SHM follows.
It is easy to observe the wave motion in a string but it doesn´t tell the whole story of wave properties. A string wave can't diffract or interfere. Sometimes simple explanations cause misunderstandings. Here a string wave is polarised by a narrow slit.
We represent a sound wave by drawing lines like the coils of a slink spring but we should remember that although layers of air oscillate the individual atoms do not.
Since there is no energy transfer the pendulum wave isn't really a wave but it looks impressive. Waves motion can be represented by graphs but be careful, a graph is a graph not a picture of the wave.
A juggler may not understand the mathematical representation of phase but the are using the effect as they throw balls in the air at different times. It is important to understand the concept of phase before starting the waves section.
Wave simulations use the same mathematical equations that are used to model real waves so have the same properties. Here a ripple tank simulation will be used to show how waves reflect, refract, interfere and diffract.