physics 20. the importance of waves waves are everywhere around us many times when we think about...
TRANSCRIPT
WavesPhysics 20
The Importance of Waves
Waves are everywhere around us
Many times when we think about waves we initially think about waves we see in the ocean
However most waves that are in our everyday lives are waves that we cannot physically see with our eyes
Think about dolphins and bats...
How do bats see in the dark and know where they are flying?
How do dolphins who are blindfolded still retrieve objects, how do they see?
Both bats and dolphins use sound waves to “see”
We also use waves in medicine; ultrasound allows humans to see a fetus or detect tumors
Radio waves carry information, while sound waves can carry conversation, and light waves stimulates the cells for vision
Think about earthquake waves, microwaves, stadium waves, water waves
Waves are a form of energy transferAll waves carry energy from one place to
anotherAll waves are travelling disturbances
Disturb: to interrupt, to interfere with, unsettle
Medium: an intervening substance, such as air or water
A wave is a transfer of energy in the form of a disturbance, through a medium
A wave can be created by vibrations that create disturbances
A pulse is a single disturbance . Therefore a wave is a repeating and periodic disturbance through a medium that moves from one location to another
To understand a wave you need to think about the medium as being a collection of interacting particles
The interactions of one particle of the medium with the next adjacent particle allow the disturbance to travel through the medium.
Transferring energyWaves are said to be an energy transport
phenomenon. As a disturbance moves through a medium from one particle to its adjacent particle, energy is being transported from one end of the medium to the other.
Transporting energy NOT matterIn a wave phenomenon, energy can move
from one location to another, yet the particles of matter in the medium return to their fixed position. A wave transports its energy without transporting matter.
Waves are seen to move through an ocean or lake; yet the water always returns to its rest position. Energy is transported through the medium, yet the water molecules are not transported. Proof of this is the fact that there is still water in the middle of the ocean. The water has not moved from the middle of the ocean to the shore. If we were to observe a gull or duck at rest on the water, it would merely bob up-and-down in a somewhat circular fashion as the disturbance moves through the water. The gull or duck always returns to its original position. The gull or duck is not transported to the shore because the water on which it rests is not transported to the shore. In a water wave, energy is transported without the transport of water.
Types of WavesWe will be studying two types of waves:
TransverseLongitudinal
Transverse WaveA transverse wave is a wave in which
particles of the medium move in a direction perpendicular to the direction that the wave moves
A longitudinal wave is a wave in which particles of the medium move in a direction parallel to the direction that the wave moves.
Sound waves are a good example of longitudinal waves
Earthquakes are capable of producing both longitudinal and transverse waves
Properties of Transverse WavesThink about a wave made by a stone thrown
into a lakeThe water would be the mediumThe part of the water that is not disturbed by
the wave is known as the equilibrium position
The region where the water rises above the equilibrium position is known as the crest
The regions where the water is lower than the equilibrium position are known as troughs
Wave Properties Cont’dAmplitude is the distance from the
equilibrium position to the top of a crest or the bottom of a trough
The wavelength is the horizontal length of one cycle of the wave. It is measured from crest to crest or trough to trough. It is the distance between any two successive points on the wave
Properties of a Longitudinal WavesA region where the coils are spread apart,
thus maximizing the distance between coils, is known as a rarefaction
A compression is a region where the coils are pressed together in a small amount of space
Period: is the time required to take one complete cycle
Frequency: refers to how often the particles of the medium vibrate when a wave passes through the medium
Frequency refers to how often something happens. Period refers to the time it takes something to happen. Frequency is a rate quantity. Period is a time quantity. Frequency is the cycles/second. Period is the seconds/cycle.
Mathematically, the period is the reciprocal of the frequency and vice versa. In equation form, this is expressed as follows
Period= 1/frequency Frequency= 1/period
Since the symbol f is used for frequency and the symbol T is used for period, these equations are also expressed as:
T= 1/f f=1/T
Time to try some examples!!