WAVES
Properties of Waves
All waves carry energy from one point to another
without transferring matter.
As an example, when sound travels through air the
air molecules don’t actually travel all the way
from the point of origin of the sound to the point
where it is heard by an individual.
The atoms only vibrate back and forth transferring
mechanical energy.
Can sound travel in a vacuum?
N0! If there aren’t any air molecules there is nothing
present in which the energy can be transferred.
Types of Waves:
Waves are categorized as either transverse or
longitudinal.
In the case of longitudinal waves the matter vibrates
parallel to the direction of energy movement.
In the case of transverse waves, the matter vibrates
perpendicular (at right angles to) the direction of
energy flow.
Sound is an example of a longitudinal wave.
An ocean wave is an example of a type of transverse
wave.
All electromagnetic waves are transverse waves.
Electromagnetic Waves:
If all electromagnetic waves are transverse
waves then how do X-rays differ from red
light?
To understand this you must be familiar with
terms regarding waves.
Wavelength: is the distance from a given point
on a wave to the next similar point on the
wave. This is usually measured from peak to
the next similar peak.
Speed: this is the speed at which the wave
travels
Frequency: is the number of wave crests which
Note how the characteristics of
waves relates to the wave below.
Wavelength
Amplitude
As the wavelength of a wave
decreases, how is the frequency
effected?
If the speed of the wave remains the same while the
wavelength is shortened, the number of crests
passing by per second would increase.
This is the major reason why waves of the same type
differ from one another.
As an example, not all sound is at the same pitch.
All sound travels at the same speed but due to
different wavelengths, the waves have different
frequencies.
Frequency determines pitch. The higher the
frequency the higher the pitch.
If you were to change the
amplitude of a wave would
this effect the other properties
of the wave?
No, the amplitude would not effect the speed, or
the wavelength.
The main characteristic which would be altered
is the volume.
A sound wave with large amplitude is “Loud”.
A light wave with large amplitude is “Bright”.
What type of wave are each of
the following?
X-Ray
Sound Wave
Blue Light
Radio Waves
Transverse
Longitudinal
Transverse
Transverse
Which property of a wave
determines the following for
sound?
Volume
Amplitude
Pitch
Wavelength
The Doppler Effect:
The Doppler effect is the change in the perceived
pitch of sound due to either the motion of the
observer or the sound generator.
Anytime an object making sound is moving towards
you, you will perceive the pitch of the sound at a
higher frequency than it is actually being
produced.
As an example, a frequency of 256 Hz is middle C
on a musical scale. If a car is honking its horn,
which is producing a frequency of middle C, and
at the same time driving towards you, you will
actually hear this sound at a higher frequency
The Doppler Effect:
If the car honking its horn is moving away from you
you will perceive the pitch of the horn at a lower
frequency than it is actually being generated.
This is also true if you the observer are moving and
the sound generator is at rest.
If you are moving towards the car you will hear the
pitch of the horn at a higher frequency
If you are moving away from the stationary car you
will hear the pitch of the horn at a lower
frequency.
The Doppler Effect:
In general, you measure the relative motion
between two objects to determine if the
pitch would be higher or lower.
If the relative motion is “moving away from
each other” , the pitch will be lower.
If the relative motion is “moving closer
together”, the pitch will be higher.
Determine whether the objects would hear
the sound at a frequency higher or lower
than it is being generated.
Van hears sound of sports car at
Sports car hears sound of Fire Engine
Fire engine hears sound of sports car at
Sports Car hears sound of jet at
Jet hears sound of Sports Car at
Higher pitch
Lower pitch
Lower pitch
Higher pitch
Higher Pitch
Speed = 400mi/hr
Speed = 35mi/hr
Speed = 35mi/hr
Speed = 60mi/hr