Part 1 - Upper Sandusky High School

cypriotcamelUrban and Civil

Nov 29, 2013 (3 years and 9 months ago)

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Waves

Transverse & Longitudinal Waves

First lets look at Vibrations

A wave is a vibration that carries energy from one place to another. But not
all vibrations are waves.

Hold a pen lightly between your thumb and index finger. Shake your hand
back and forth to make the pen seem to bend like it’s made of rubber.
Next, hold a length of string (about 1 meter long) at one end. Shake the
end of the string back and forth. Observe the vibrations.


1.

Describe the motion of the



pen and the motion of



the string.


2.

In which case did the vibration



move from one place to another? In which



case did the vibration stay in one place?


What is a Wave?


Definition of a wave


a disturbance that travels through a medium from
one location to another location



The Medium


the substance or material which carries the wave


medium can be any material which transfers
energy of the disturbance


can even be transmitted through a vacuum


ex. light

Types of Waves


sound waves


visible light waves


radio waves


microwaves


water waves


sine waves


cosine waves


telephone chord
waves


stadium waves


earthquake waves


waves on a string


slinky waves


The Medium


Medium transfers wave energy but has no movement
itself


waves which require a medium are called mechanical waves


energy is transferred, however, matter is not

The Medium


(cont.)


Factors which affect energy transfer


density of the material


as density increases, speed decreases


this is due to the inertia of the object


more matter to = more inertia to overcome


elasticity of the material


ability to return to its original shape after being
disturbed


waves move faster in more elastic mediums


speed is faster in steel than in air

The Slinky


The natural state something exists in is known as


equilibrium

or
rest position


spacing is equally far apart


Disturbance

occurs


first particle moves from equilibrium


may move up, down, forward, or backward

The Slinky


Wave Pulse


is the observed motion of a
single

disturbance


Wave


is a repeating & periodic disturbance which moves
through a medium from one location to another

Classification of Waves


Waves are classified depending on the
movement of the medium as compared
to the movement of the wave



Classifications


transverse


longitudinal


surface

Direction of motion

Transverse Waves


Motion of the medium is at right angles to the
direction of the wave



dashed line represents the equilibrium or rest
position

Parts of a transverse wave


Parts of a transverse wave


“an up and
down wave”



Crest


highest point


maximum displacement
upward of a particle in the medium


Trough


maximum displacement downward

Another view

Transverse Wave in Action


Examples of Transverse Waves


a stadium wave


strings on a guitar


strings in a piano

Parts of a Longitudinal Wave


Compressions


space in medium in which particles are
crowded


max. density


particles collide with particles next them


Rarefactions


space in medium in which particles are not
crowded


min. density

Longitudinal Waves


Longitudinal waves


series of compressions and rarefactions in a
medium


move in direction parallel to the direction of energy
transport


Another Look

Longitudinal Waves in action

The above animation portrays a medium as a series of particles
connected by springs.


As one individual particle is disturbed, it transmits the disturbance to
the next interconnected particle.


This disturbance continues to be passed on to the next particle.


The result is that energy is transported from one end of the medium
to the other end of the medium without the actual transport of matter.


In this type of wave
-

a longitudinal wave
-

the particles of the medium
move in a direction parallel to the direction of energy transport.

Typical mediums for

Longitudinal Waves


Materials that usually transmit only
longitudinal waves:


fluids


liquids


gases


plasmas



Sound wave are examples of
longitudinal waves

Tuning Forks


longitudinal waves


A tuning fork is an instrument


which produces sound by means


of a vibrating object.



Once stuck the tines produce a


disturbance of surrounding air


molecules.



As the tines compress together they produce a high pressure region


next to the tine and visa versa.



The air molecules appear to move forward, however, they only vibrate


back and forth carrying the energy on to the next air molecule.



In solids, sound can exist as either longitudinal or transverse.



In fluids, however, sound can only exist as longitudinal.

Guitar Strings produce

Longitudinal Waves


sound is produced by a



vibrating object



as the stings vibrate so does


the surrounding air



the frequency at which the air molecules vibrate are equal to that of the
string



the vibration causes high & low pressure regions like the tuning fork
producing sound waves



the string itself doesn’t produce much sound so it is attached to a box
where the air inside vibrates at the same frequency for a louder sound


Ear Drums


longitudinal waves


as a sound wave travels


through a fluid medium it


vibrates in a direction parallel


(an anti
-
parallel) to the direction which


the sound travels



so if it moves from west to east it also moves from east to west



as it causes a displacement by compression a high pressure region is
created



a restoring force typically pulls each particle back to its rest position



as they are pulled away a low pressure region is created



this movement back and forth is known as a pressure wave

Ear Drums


How it works

Sound waves travel through the
canal of the external ear...

and vibrates the ear drum…

which divides the external ear

from the middle ear.

The middle ear’s 3 bones

Malleus, Incus, Stapes)…

transmit the energy of sound

vibrations to the fluids in the inner ear

Vibrations in this fluid stimulate the

delicate nerve hair cell fibers.

Finally, the hearing nerve transmits

impulses or signals to the brain

to be interpreted as understandable

sound.

Surface Wave

Combination of Waves
-

Surface


Water waves are an example of waves that involve a
combination of longitudinal and transverse motions.


As a wave travels through the water, the particles
travel in
clockwise circles
.


the blue particles demonstrates the clockwise motion
as the wave passes

The End

Transverse & Longitudinal Waves