Transcript Wave Properties + Light & Sound

Wave Properties
Waves In General:
• Waves are energy traveling
through a “medium” (solid,
liquid or gas material)
• Properties of waves
depend on elasticity of the
medium:
Sound speeds in
different mediums
Air (0 degrees) 331 m/s
Air
(20 degrees)
343 m/s
As you can see, sound travels
at different speeds depending
on the medium
Water
1500 m/s
Think: Why would waves
move through solids faster
than a gas like “air”?
Iron
4400 m/s
Glass
5100 m/s
Sound Travel in “Space”:
So if the astronauts communications device fails,
If there
Think:
isn’t
What
enough
is missing
atomsfor
(“air”)
the energy
out there,
of
So can
any sounds
out there
all? the
can they
takethere
theirbe
helmets
off (don’t
worryat
about
can the sound to
energy
travelactual
between
travel
them?
anywhere?
whole “breathing” thing here) and just talk?
Properties of Waves:
They may not look like much, but waves have several features that we
use to describe what result the energy will have:
Wavelength:
Wavelength: The distance between any point on a
wave and the equivalent point on the next phase.
Literally, the length of the wave.
It is either the distance between
two different tops of waves
Or the distance between
two different bottoms of waves,
either way, it will be the same!
Amplitude:
Amplitude: The strength or power of a wave signal.
The "height" of a wave when viewed as a graph.
The Amplitude is the height of a
wave from bottom to top
Amplitude = Loudness
How we sense Amplitude = Loudness
Higher amplitudes are interpreted as a higher volume, hence the name
"amplifier" (or “amp’s”) for a device which increases amplitude.
More Amplitude means more height!
Less Amplitude means less height!
Think: Which wave will have a louder sound?
Frequency:
Frequency: The number of times the wavelength occurs in one
second. (Like waves per second)
The faster the sound source vibrates, the faster the wave and
the “higher” the frequency.
1 second
Low
High
How Frequency Affects Sound:
How we sense Frequency = “Pitch”
Higher frequencies are interpreted by our brain as a higher pitch.
For example; when you sing in a high-pitched voice you are forcing
your vocal chords to vibrate quickly.
(Also note that high frequency = high energy.)
“High” note = High Frequency
“Low” note = Low Frequency
Our ears are sensitive to sound energy. We perceive a high
Notice:
Did as
the
Amplitude
when
we changed
frequency?
frequency
a high
pitched change
note; a low
frequency
as a lowthe
pitched
note.
“Light” Spectrum: A graph that shows the
different frequencies of light waves and
the resulting types of light and colors.
Light Frequency = Type of light and color
Higher frequencies are interpreted as different types light. For
example; a higher frequency can make a darker color.
Radio | Micro | Infra Red | Visible Light | UV | X-Ray | Gamma
Notice that low Frequencies
make radio, micro, and Infrared
waves of energy
Also different Frequencies
make colors. This is the only
type of light Humans can see.
Higher Frequencies
make Ultraviolet, X ray, and Gamma
waves of energy
Lastly: Notice that all
These Waves have the
same amplitude!
So what is White Light?
White Light is actually made up of many different
colors – each color is made up of its own frequency
and wavelength.
When you combine the colors together
it actually makes white light!
You can shine white light into a prism
and it separates it out into the mix of colors
Notice the white
light coming in
Notice the split
spectrum coming out.
Wave Speed:
• Average Wave Speeds: can vary
depending on the type of energy
8
3.0x10 m/s
Light =
Sound ≈ 340 m/s
(Faster than most jets)
Of course it still depends on what medium the Energy is travelling through!!!
Why we see the firework first – then hear it after?
Light travels faster than Sound!!!
Hammering
It takes longer for the sound energy
To reach your ear than for the light
Energy to reach your eye!
That’s why we can see something
before we can hear it!
Since waves propagate in 3D, we can see
the light from this candle in all directions.
Same thing applies with sound.
Wave motion is like an onion:
Spreads out in all directions
equally!
Think about it; is there any direction (up down, left, right…etc…)
that the sun DOESN’T shine it’s light and heat energy?
Intensity: The further out you go from the energy source, the less intense the wave is.
The reason the farther out planets are “colder” is because they are farther from the
source of the heat and light in our solar system.
EX: If you wanted to save your ears from the loudness of the speakers – scoot back!
Movement of Waves:
The layers of an onion, are a good representation of how waves look as they travel
In every direction equally at the same time!
HEY! I’ve
got layers
too!!!
The exception is “surface waves” (like wind generated ocean
waves). They only travel on a “surface” (not up and down).
Common Instruments we use to
sense light energy in our lives
Glasses
Telescope
MRI Machine
Satellite Dish
Common Instruments we use to
sense light energy in our lives
Microphone
Hearing Aid
Sonar
Stethoscope
Ultrasound