Light and Sound

Wave A disturbance in a medium that transfers energy from one location to another

Types of Waves There are three main types of waves that we know of in our universe: 1.Mechanical Waves 2.Electromagnetic Waves 3.Matter Waves We will study only the first two types

Mechanical Waves 1.Examples include sound waves, water waves, earthquake tremors, vibrating strings, etc. 2.Key Feature: Mechanical waves must travel through matter. They cannot travel in a vacuum. For example, there is no sound in space (a vacuum). If you’ve ever seen the movie Alien, its tagline is “In space, no one can hear you scream). 3.Mechanical waves travel faster as the density of the medium increases. This means, for example, that sound travels faster in water than in air, which explains why whales can hear each other over distances of hundreds of kilometres. 4.Mechanical waves transfer energy by causing particles in the medium to vibrate. The greater the vibration, the greater the energy they carry.

Electromagnetic Waves 1.Examples include: light (visible, ultraviolet, infrared), x-rays, radio waves, gamma rays, etc. 2.Key Feature: All electromagnetic waves travel at the speed of light, 3.00 * 10 8 m/s when in a vacuum. They slow down as the density of a medium increases. For example, light does not travel as well through water as air, thus it appears darker underwater. 3.An electromagnetic wave does not need matter to travel in because it carries its own energy in particles called photons. These photon particles travel in a wave-like pattern, giving electromagnetic radiation a dual wave-particle nature. 4.All forms of electromagnetic radiation make up what is known as the electromagnetic spectrum.

Sub-Categories of Mechanical Waves There are three types of mechanical waves: 1.Transverse Waves – Has the appearance of a typical sine wave. A example is a vibrating guitar string. The particles of the medium vibrate perpendicular to the flow of energy. 2.Longitudinal Waves – The particles of the medium vibrate parallel to the flow of energy. Sound is an example of a longitudinal wave. This type of wave is composed of regions of high pressure called ‘compressions’ and low pressure called ‘rarefactions’ and is thus often called a pressure wave. 3.Surface Waves – Surface waves are a combination of both longitudinal and transverse waves. A common example is the water wave. A water wave is transverse along the surface, where up and down vibration is possible, and longitudinal at depth.