# Part 1 - Upper Sandusky High School

Urban and Civil

Nov 29, 2013 (4 years and 5 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