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Periodic Motion In Physics, a motion that is regular and repeating is referred to as a periodic motion. Most objects that vibrate do so in a regular and repeated fashion; their vibrations are periodic. Examples are the motion of the swing, the bouncing up and down of a spring, or the vibration of a string in a guitar.
Waves and Wavelike Motion Waves are everywhere. Whether we recognize it or not, we encounter waves on a daily basis. 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. 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. The motion of a pendulum, the motion of a mass suspended by a spring, the motion of a child on a swing, and the wave of the hand can be thought of as wavelike phenomena.
CHARACTERISTICS OF WAVES - a wave can be described as a disturbance that travels through a medium from one location to another location. - a wave medium is the substance that carries a wave (or disturbance) from one location to another. The wave medium is not the wave and it doesn't make the wave; it merely carries or transports the wave from its source to other locations.
The crest of a wave is the point on the medium that exhibits the maximum amount of positive or upward displacement from the rest position. The trough of a wave is the point on the medium that exhibits the maximum amount of negative or downward displacement from the rest position.
The amplitude of a wave refers to the maximum amount of displacement of a particle on the medium from its rest position. In a sense, the amplitude is the distance from rest to crest. Similarly, the amplitude can be measured from the rest position to the trough position. The wavelength of a wave is simply the length of one complete wave cycle. The wavelength can be measured as the distance from crest to crest or from trough to trough.
The frequency in a wave gives you the number of wavelengths passing through a point, or the number of cycles per unit time Another unit for frequency is the Hertz (abbreviated Hz) where 1 Hz is equivalent to 1 cycle/second. The period in a wave gives you the time it takes for the wave to move through one wavelength, or one cycle
Speed in a wave tells us how fast it travels in a medium Since the period is the reciprocal of the frequency, the expression 1/f can be substituted into the above equation for period. Rearranging the equation yields a new equation of the form: Speed = Wavelength • Frequency Frequency = Number of Complete Waves / Time
Kinds of Waves A transverse wave is a wave in which particles of the medium move in a direction perpendicular to the direction that the wave moves. - Examples are light waves and other electromagnetic waves A longitudinal wave is a wave in which particles of the medium move in the same direction that the wave moves. - Examples are sound waves and some seismic (earthquake-generated) waves
Wave Changes Reflection, refraction and diffraction are all boundary behaviors of waves associated with the bending of the path of a wave. The bending of the path is an observable behavior when the medium is a two- or three-dimensional medium. Reflection occurs when there is a bouncing off of a barrier. Reflection of waves off straight barriers follows the law of reflection. Reflection of waves off parabolic barriers results in the convergence of the waves at a focal point. Refraction is the change in direction of waves that occurs when waves travel from one medium to another. Refraction is always accompanied by a wavelength and speed change. Diffraction is the bending of waves around obstacles and openings. The amount of diffraction increases with increasing wavelength.
Interference Wave interference is the phenomenon that occurs when two waves meet while travelling along the same medium.
Constructive interference is a type of interference that occurs at any location along the medium where the two interfering waves have a displacement in the same direction. In this case, both waves have an upward displacement; consequently, the medium has an upward displacement that is greater than the displacement of the two interfering pulses.
Destructive interference is a type of interference that occurs at any location along the medium where the two interfering waves have a displacement in the opposite direction.
