Download Wavelength

Parts of a Wave
Frequency = 2 waves per second
Crest
Wavelength
Normal
Rest
Position
Trough
Wavelength
What does each part of the wave mean?
Crest – highest point of a wave
Trough - lowest point of a wave
Wavelength – the distance between two crests or two
troughs
Frequency – how many wavelengths pass a fixed
point each second
– Expressed in Hertz (Hz)
– As frequency increases, wavelength decreases
Amplitude – height of a wave, or the amount of energy
in a wave
Rest position (equilibrium) – describes a wave at rest,
not passing on energy
http://phet.colorado.edu/sims/wave-on-a-string/waveon-a-string_en.html
Properties of Sound
Loudness is an important property of sound
Loudness refers to your perception of the energy
of a sound
Loudness of a sound depends on two factors:
– The amount of energy it takes to make the sound
– The distance from the source of the sound
In general, the greater the energy used to make
a sound, the louder the sound
Ex: the harder you pluck the strings of a guitar,
the louder the sound
Intensity
The more energy used
to pluck the string, the
greater the amplitude
of the wave, and the
more intense the sound
Recall that amplitude is
the height of a wave; and
the amount of energy in
a wave
Intensity is the amount
of energy in a sound, or
loudness
– As amplitude increases,
intensity increases
– As amplitude decreases,
intensity decreases
Loudness in Decibels (db)
The loudness of different sounds is compared using a unit
called the decibel (db)
The greater the intensity of a sound, the higher the
decibels (db The loudness of a sound you can barely hear
is about 10 db
Each 10-db increase in loudness represents a tenfold
increase in the intensity of the sound
For example, soft music at 30 db sounds ten times louder
than a 20-db whisper
The 30-db music is 100 times louder than the 10-db sound
of rustling leaves
Sounds louder than 100 db can cause damage to your
ears, especially if you listen to those sounds for long
periods of time
120 db is the loudness level that can actually cause pain
to your ears
Intensity vs. Distance from the Source
Because sound waves
spread out in all
directions, intensity
decreases as the
distance between you
an the source
increases
A sound wave of
greater intensity
sounds louder
As you move away
from the source,
loudness decreases
because the intensity
decreases
3 m, the
At 2 m, the ear hears a sound with ¼At
of
the
intensity has
decreased to 1/9
intensity
At 2 m, the
ear hears a heard at 1m
of the intensity
sound with ¼ of the
at 1m.
At 3m,
the intensity has decreased to
1/9
intensity heard at 1m.
of the intensity at 1m
Speaker