waves and waves properties

1. Waves and Wave Properties
Waves and Wave Properties

2. A wave is a disturbance that carries
energy from place to place.
A wave does NOT carry matter with
it! It just moves the matter as it goes
through it.

3. Some waves do not need matter
(called a “medium”) to be able to
move (for example, through space).
These are called electromagnetic
waves (or EM waves).
Some waves MUST have a medium
in order to move. These are called
mechanical waves.

4. Wave Types
1.Transverse waves: Waves in which the medium
moves at right angles to the direction of the wave

5. Parts of transverse waves:
Crest: the highest point of the wave
Trough: the lowest point of the wave

6. 2. Compressional (or longitudinal) waves:
Waves in which the medium moves back and
forth in the same direction as the wave

7. Parts of longitudinal waves:
Compression: where the particles are close together
Rarefaction: where the particles are spread apart

8. NSF North Mississippi GK-8
NSF North Mississippi GK-8 8
8
The Electromagnetic Spectrum
The Electromagnetic Spectrum
Different
Different
wavelengths of EM
wavelengths of EM
waves.
waves.
These wavelengths
These wavelengths
of light and others
of light and others
make up a
make up a
spectrum.
spectrum.

9. Wave Properties
Wave properties depend on what
(type of energy) is making the waves.
1.Wavelength: The distance between one point
on a wave and the exact same place on the
next wave.

10. 2. Frequency: How many waves go past a point in
one second; unit of measurement is hertz (Hz).
The higher the frequency, the more energy in the
wave.
10 waves going past in 1 second = 10 Hz
1,000 waves go past in 1 second = 1,000 Hz
1 million waves going past = 1 million Hz

11. 3. Amplitude: How far the medium moves from
rest position (where it is when not moving).
Remember that for transverse waves, the highest
point is the crest, and the lowest point is the trough.

12. Remember that for compressional waves, the points where the medium is
close together are called compressions and the areas where the medium is
spread apart are called rarefactions.
The closer together and further apart the particles are, the larger the amplitude.
compression
rarefaction

13. Properties of Sound
Properties of Sound
〉What are the characteristics of sound
What are the characteristics of sound
waves?
waves?
〉sound wave:
sound wave: a longitudinal wave that is
a longitudinal wave that is
caused by vibrations and that travels through
caused by vibrations and that travels through
a material medium
a material medium
In air, sound waves spread out in all
In air, sound waves spread out in all
directions away from the source.
directions away from the source.

14. Properties of Sound,
Properties of Sound,
continued
continued
The speed of sound depends on the
The speed of sound depends on the
medium.
medium.
• The speed of sound in a particular medium
The speed of sound in a particular medium
depends on how well the particles can transmit
depends on how well the particles can transmit
the motions of sound waves.
the motions of sound waves.
• Sound waves travel faster through liquids and
Sound waves travel faster through liquids and
solids than through gases.
solids than through gases.

15. Properties of Sound,
Properties of Sound,
continued
continued
Speed of Sound in Various Mediums
Speed of Sound in Various Mediums

16. Speed of Sound
Speed of Sound

17. Properties of Sound,
Properties of Sound,
continued
continued
Loudness is determined by intensity.
Loudness is determined by intensity.
– loudness
loudness:
: depends partly on the energy contained in
depends partly on the energy contained in
the sound wave
the sound wave
– intensity:
intensity: describes the rate at which a sound wave
describes the rate at which a sound wave
transmits energy through a given area of a medium
transmits energy through a given area of a medium
– Intensity depends on
Intensity depends on
the amplitude of the sound wave
the amplitude of the sound wave
your distance from the source
your distance from the source
– The greater the intensity of a sound, the louder the
The greater the intensity of a sound, the louder the
sound will seem.
sound will seem.
Intensity is measured in units called
Intensity is measured in units called decibels
decibels, dB.
, dB.

18. Sound Intensity and Decibel
Sound Intensity and Decibel
Level
Level

19. Properties of Sound,
Properties of Sound,
continued
continued
Pitch is determined by frequency.
Pitch is determined by frequency.
• pitch:
pitch: a measure of how high or low a sound is
a measure of how high or low a sound is
perceived to be, depending on the frequency of the
perceived to be, depending on the frequency of the
sound wave
sound wave
• A high-pitched sound corresponds to a high
A high-pitched sound corresponds to a high
frequency.
frequency.
• A low-pitched sound corresponds to a low
A low-pitched sound corresponds to a low
frequency.
frequency.

20. THANK YOU

21. Pitch
Pitch

22. Properties of Sound,
Properties of Sound,
continued
continued
Humans hear sound waves in a limited
Humans hear sound waves in a limited
frequency range.
frequency range.
– Any sound with a frequency below the range of
Any sound with a frequency below the range of
human hearing is known as an infrasound.
human hearing is known as an infrasound.
infrasound:
infrasound: slow vibrations of frequencies lower than
slow vibrations of frequencies lower than
20 Hz
20 Hz
– Any sound with a frequency above human
Any sound with a frequency above human
hearing range is known as an ultrasound.
hearing range is known as an ultrasound.
ultrasound:
ultrasound: any sound wave with frequencies higher
any sound wave with frequencies higher
than 20,000 Hz
than 20,000 Hz

23. Comparing Infrasonic and
Comparing Infrasonic and
Ultrasonic Sounds
Ultrasonic Sounds

24. Musical Instruments
Musical Instruments
〉How do musical instruments
How do musical instruments
make sound?
make sound?
〉Most instruments produce sound
Most instruments produce sound
through the vibration of strings,
through the vibration of strings,
air columns, or membranes.
air columns, or membranes.

25. Musical Instruments
Musical Instruments
Musical instruments rely on standing
Musical instruments rely on standing
waves.
waves.
– Standing waves can exist only at certain
Standing waves can exist only at certain
wavelengths on a string.
wavelengths on a string.
– The primary standing wave on a vibrating
The primary standing wave on a vibrating
string has a wavelength that is twice the
string has a wavelength that is twice the
length of the string.
length of the string.
The frequency of this wave is called the
The frequency of this wave is called the
fundamental frequency.
fundamental frequency.

26. Fundamental Frequency
Fundamental Frequency

27. Musical Instruments,
Musical Instruments,
continued
continued
Instruments use resonance to amplify sound.
Instruments use resonance to amplify sound.
– Resonance:
Resonance: a phenomenon that occurs when
a phenomenon that occurs when
two objects naturally vibrate at the same
two objects naturally vibrate at the same
frequency
frequency
natural frequencies:
natural frequencies: the specific frequencies
the specific frequencies
at which an object is most likely to vibrate
at which an object is most likely to vibrate
– The natural frequency of an object depends on
The natural frequency of an object depends on
the object’s shape, size, mass, and the material
the object’s shape, size, mass, and the material
from which the object is made.
from which the object is made.

28. Resonance (Frequency)
Resonance (Frequency)

29. 〉How do ears help humans hear sound waves?
How do ears help humans hear sound waves?
〉The human ear is a sensitive organ that
The human ear is a sensitive organ that
senses vibrations in the air, amplifies them,
senses vibrations in the air, amplifies them,
and then transmits signals to the brain.
and then transmits signals to the brain.
Vibrations pass through three regions in the ear.
Vibrations pass through three regions in the ear.
– Your ear is divided into three regions—outer, middle, and
Your ear is divided into three regions—outer, middle, and
inner.
inner.
Hearing and the Ear
Hearing and the Ear

30. Resonance occurs in the inner ear.
Resonance occurs in the inner ear.
– A wave of a particular frequency causes a
A wave of a particular frequency causes a
specific part of the basilar membrane to vibrate.
specific part of the basilar membrane to vibrate.
– Hair cells near the part of the membrane that
Hair cells near the part of the membrane that
vibrates then stimulate nerve fibers that send an
vibrates then stimulate nerve fibers that send an
impulse to the brain.
impulse to the brain.
Hearing and the Ear,
Hearing and the Ear,
continued
continued

31. The Ear
The Ear

32. 〉How are the reflections of sound waves
How are the reflections of sound waves
used?
used?
〉Reflected sound waves are used to
Reflected sound waves are used to
determine distances and to create images.
determine distances and to create images.
Some ultrasound waves are reflected at
Some ultrasound waves are reflected at
boundaries.
boundaries.
Ultrasound and Sonar
Ultrasound and Sonar