IB Physics Sub-topic C2 Notes
Travelling waves
In Topic C.1, you learned about simple harmonic motion. Remember that waves are one of the examples of oscillations that exhibit SHM. In this topic, you learned about a particular type of wave that does this, called a travelling wave.
A travelling wave is defined as an oscillating wave that transfers energy through a medium via the movement of particles in the direction of the wave. These waves always have a constant speed (v) that is dependent on wave frequency (f) or period (T) and wavelength (λ)
However, particles can move in two directions, forming either transverse waves or longitudinal waves. Let’s cover each one now.
Transverse waves
In transverse waves, the oscillation is perpendicular to the direction of energy transfer. Thus, if the energy is moving left to right, the particles only move up and down.
In these, the particles only move up and down from their mean position to create the wave shape. However, the energy travels perpendicular to this, in the direction of the wave.
Common examples include water waves and light. However, light is special because it is composed of two transverse waves: an electric wave and a magnetic wave, collectively termed an electromagnetic wave.
Electromagnetic wave are also known as electromagnetic radiation, which are a form of energy that travel as a wave. Whilst all electromagnetic radiation has a speed of 3 x 108 ms-1, wavelength (λ), and frequency (f) change to give different wave types and energies. These are all described by the electromagnetic spectrum.
The different types are radio waves, microwaves, infrared radiation, visible light, ultraviolet light, X-rays, and gamma radiation. These can be remembered using the mnemonic Red Martians Invaded Venus Using X-ray Guns.
Additionally, it in this spectrum, it is important to notice that as you progress from radio waves to gamma rays:
- As wavelength decreases, frequency increases.
- As wavelength decreases, energy increases.