The process continues, as each consecutive row becomes involved by a momentary standing up and sitting back down. Beginning in Section 1, the first row of fans abruptly rise up to begin the wave as they sit back down, row 2 begins its motion as row 2 sits back down, row 3 begins its motion. The observable ripple results when a group of enthusiastic fans rise up from their seats, swing their arms up high, and then sit back down. When performed with reasonably good timing, a noticeable ripple is produced that travels around the circular stadium or back and forth across a section of bleachers.
The thought of waves often brings to mind a recent encounter at the baseball or football stadium when the crowd enthusiastically engaged in doing the wave. These mental pictures of water waves are useful for understanding the nature of a wave and will be revisited later when we begin our formal discussion of the topic. Or the waves may be circular waves that originate from the point where the disturbances occur such circular waves travel across the surface of the water in all directions. The waves may appear to be plane waves that travel together as a front in a straight-line direction, perhaps towards a sandy shore. A duck or gull at rest on the surface of the water is observed to bob up-and-down at rather regular time intervals as the wave passes by. Every crest is separated by a trough to create an alternating pattern of crests and troughs. One crest is often followed by a second crest that is often followed by a third crest. The water wave has a crest and a trough and travels from one location to another. The waves are created by some form of a disturbance, such as a rock thrown into the water, a duck shaking its tail in the water or a boat moving through the water. Where do we see waves or examples of wavelike motion? What experiences do we already have that will help us in understanding the physics of waves?įor many people, the first thought concerning waves conjures up a picture of a wave moving across the surface of an ocean, lake, pond or other body of water. Before beginning a formal discussion of the nature of waves, it is often useful to ponder the various encounters and exposures that we have of waves. We study the physics of waves because it provides a rich glimpse into the physical world that we seek to understand and describe as students of physics. Waves (and wavelike phenomena) are everywhere! The motion of a pendulum, the motion of a mass suspended by a spring, the motion of a child on a swing, and the "Hello, Good Morning!" wave of the hand can be thought of as wavelike phenomena.
In addition to waves, there are a variety of phenomena in our physical world that resemble waves so closely that we can describe such phenomenon as being wavelike. Sound waves, visible light waves, radio waves, microwaves, water waves, sine waves, cosine waves, stadium waves, earthquake waves, waves on a string, and slinky waves and are just a few of the examples of our daily encounters with waves.
Whether we recognize it or not, we encounter waves on a daily basis.