Wave PropertiesWave Properties

Waves In General:Waves In General:• Waves are energy Waves are energy

traveling through a traveling through a ““mediummedium” (solid, liquid ” (solid, liquid or gas material)or gas material)

• Properties of waves Properties of waves depend on elasticity of depend on elasticity of the medium:the medium:

Sound speeds in Sound speeds in different mediumsdifferent mediums

Air Air (0 (0 degrees)degrees)

331 m/s331 m/s

Air Air (20 (20 degrees)degrees)

343 m/s343 m/s

WaterWater 1500 m/s1500 m/s

IronIron 4400 m/s4400 m/s

GlassGlass 5100 m/s5100 m/s

As you can see, sound travels at different speeds depending

on the medium

Think: Why would waves move through solids faster

than a gas like “air”?

Sound Travel in “Space”:Sound Travel in “Space”:

So if the astronauts communications device fails, can they take their helmets off (don’t worry about the

whole “breathing” thing here) and just talk?

Think: What is missing for the energy of sound to travel between them?

If there isn’t enough atoms (“air”) out there,can the sound energy actual travel anywhere?So can there be any sounds out there at all?

Properties of Waves: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:

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 betweentwo different tops of waves

Or the distance betweentwo different bottoms of waves, either way, it will be the same!

Amplitude: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 = LoudnessAmplitude = 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?

1 second

Frequency: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.

Low

High

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.)

Our ears are sensitive to sound energy. We perceive a high frequency as a high pitched note; a low frequency as a low pitched note.

How Frequency Affects Sound:How Frequency Affects Sound:

“High” note = High Frequency

“Low” note = Low Frequency

Notice: Did the Amplitude change when we changed the frequency?

““Light” Spectrum:Light” Spectrum: A graph that shows the A graph that shows the different frequencies of light waves and the different frequencies of light waves and the resulting types of light and colors.resulting types of light and colors.

Radio | Micro | Infra Red | Visible Light | UV | X-Ray | Gamma

Light Frequency = Type of light and colorHigher frequencies are interpreted as different types light. For

example; a higher frequency can make a darker color.

Notice that low Frequencies make radio, micro, and Infrared

waves of energy

Higher Frequencies make Ultraviolet, X ray, and Gamma

waves of energy

Also different Frequencies make colors. This is the only type of light Humans can see.

Lastly: Notice that all These Waves have the

same amplitude!

So what is White Light?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 prismand it separates it out into the mix of colors

Notice the white light coming in

Notice the split spectrum coming out.

Wave Speed:Wave Speed:

• Average Wave Speeds:Average Wave Speeds: can vary can vary depending on the type of energydepending on the type of energy

Light = 3.0x10Light = 3.0x108 8 m/sm/s

Sound Sound ≈ 340 m/s≈ 340 m/s(Faster than most jets)(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!!!

HammeringHammering

It takes longer for the sound energyTo reach your ear than for the light

Energy to reach your eye!

That’s why we can see somethingbefore 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: Wave motion is like an onion: Spreads out in Spreads out in all directions all directions

equallyequally!!

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!

Think about it; is there any direction (up down, left, right…etc…)Think about it; is there any direction (up down, left, right…etc…) that the sun DOESN’T shine it’s light and heat energy?that the sun DOESN’T shine it’s light and heat energy?

Movement of Waves: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!

The exception is “surface waves” (like wind generated ocean waves). They only travel on a “surface” (not up and down).

HEY! I’ve got layers

too!!!

Common Instruments we use Common Instruments we use to sense light energy in our to sense light energy in our liveslives

Telescope

MRI Machine

Satellite Dish

Glasses

Common Instruments we use Common Instruments we use to sense light energy in our to sense light energy in our liveslives

Sonar

MicrophoneHearing Aid

Stethoscope

Ultrasound