Introduction to Waves

This topic is part of the HSC Physics course under the section Properties of Waves.

HSC Physics Syllabus

• conduct a practical investigation involving the creation of mechanical waves in a variety of situations in order to explain:

– the role of the medium in the propagation of mechanical waves
– the transfer of energy involved in the propagation of mechanical waves (ACSPH067, ACSPH070)
• conduct practical investigations to explain and analyse the differences between:
– transverse and longitudinal waves (ACSPH068)
– mechanical and electromagnetic waves (ACSPH070, ACSPH074)

What is a Wave?

Waves play a crucial role in physics, transmitting energy from one point to another without the need for the net movement of matter. A wave is a disturbance that propagates through space and time, often transferring energy. It is represented mathematically as a function of space and time.

Waves can be categorised into two primary types: mechanical waves and electromagnetic waves.

Mechanical Waves

Mechanical waves are the type of waves that require a medium to propagate. The disturbance travels via the oscillation of the particles within that medium. The most common examples are sound waves and waves in a pool of water.

Mechanical waves can be further classified into two categories: transverse and longitudinal.

Transverse Waves

In transverse waves, particles of the medium move perpendicularly to the direction of the wave (propagation direction). In simpler terms, the oscillations are at right angles to the direction of energy transfer. Waves on a string or a rope are typical examples of transverse waves.

Properties of transverse waves are discussed in detail here.

Longitudinal Waves

In contrast, longitudinal waves have particles of the medium moving parallel to the wave's direction. They oscillate along the direction of the wave's propagation, leading to areas of compressions and rarefactions (like regions of high and low pressure in a sound wave). Sound waves, which travel through air, are examples of longitudinal mechanical waves.

Properties of longitudinal waves are discussed in detail here.

Electromagnetic Waves

Unlike mechanical waves, electromagnetic waves do not require a medium to propagate. They are capable of travelling through the vacuum of space. These waves are produced by the oscillation of electric charges, which generate oscillating electric and magnetic fields.

Examples of electromagnetic waves include visible light, ultraviolet and infrared radiation, microwaves, radio waves, and X-rays. These waves differ in their frequency or wavelength, which will be discussed separately.

Electromagnetic waves are transverse non-mechanical waves. The electric and magnetic fields vibrate at right angles to each other and to the direction of propagation.