Understanding different types of wave Ride the Wave Understanding different types of wave

Good, good, good, good vibrations! http://www.youtube.com/watch?v=NwrKKbaClME

Waves are created when a source of energy (force) causes a __________. So what are vibrations? A vibration is a repeated ________ and _________ motion or ____ and _____ motion.

Waves transfer energy not matter Waves transfer energy not matter. The water waves below are carrying energy but are not moving. Waves can only exist as they have energy to carry.

How do we classify WAVES?

Waves can be classified by WHAT they move through or by HOW energy moves through them.

Classification of WAVES by WHAT they move through

Electromagnetic Waves There are two classifications for waves based on what they move through: Mechanical Waves Electromagnetic Waves

What are mechanical WAVES?

Mechanical waves are waves that can ONLY move through a medium (through matter).

Mechanical waves require the particles of the medium to vibrate in order for energy to be transferred.

What are examples mechanical WAVES?

earthquake/seismic waves sound waves water waves earthquake/seismic waves sound waves waves that travel down a rope or spring All of these examples CANNOT move through empty space.

What is EMPTY SPACE?

Empty space is space in which NO MATTER is present Empty space is space in which NO MATTER is present. Another name for this is a vacuum.

A wave moving through a medium travels at a certain speed A wave moving through a medium travels at a certain speed. This is Wave Speed. Wave speed is usually measured in meters/second, but may be measured using other distance units (such as centimeters per second).

What are electromagnetic WAVES?

Electromagnetic waves are waves that can travel through matter or empty space where matter is not present.

What are examples of electromagnetic WAVES?

radio waves microwaves infrared waves visible light ultraviolet rays X-rays

Classification of WAVES by HOW energy moves through them

There are two classifications for waves based on how energy moves through them: Longitudinal Waves Transverse Waves

What are longitudinal WAVES?

Mechanical waves in which the particles of matter in the medium vibrate by pushing together and moving apart parallel to the direction in which the wave travels are called longitudinal waves.

Compressional/ Longitudinal Wave On a compressional wave the area squeezed together is called the compression. The areas spread out are called the rarefaction. The wavelength is the distance from the center of one compression to the center of the next compression.

http://www.lcse.umn.edu/specs/labs/glossary_items/rarefaction_spring.html

The place on the wave that is pushed together is called the compression and the place that is moving apart is the rarefaction.

What are examples of compressional/ longitudinal waves?

some seismic waves (earthquake waves- primary waves, to be exact) sound waves some waves in a spring some seismic waves (earthquake waves- primary waves, to be exact)

What is sound? Sound is a compressional wave which travels through the air through a series of compressions and rarefactions.

“Seeing Sound”

Sound travels through different media. We hear sound which usually travels through air. Sound travels through other media as well, such as water and various solids. Sound travels different speeds in different media. Sound typically travels faster in a solid that a liquid and faster in a liquid than a gas. The denser the medium, the faster sound will travel. The higher the temperature, the faster the particles of the medium will move and the faster the particles will carry the sound.

What are transverse WAVES?

Mechanical waves in which the particles of matter in the medium vibrate by moving back and forth and perpendicular (at right angles) to the direction the wave travels are called transverse waves.

science.hq.nasa.gov/kids/imagers/ems/waves3.html

The highest point of a transverse wave is the crest and the lowest point is called a trough.

What is wavelength? What is wave frequency? Wavelength is a measure of distance, so the units for wavelength are always distance units, such as meter, centimeters, millimeters, etc. What is wave frequency? Frequency is the number of waves that pass through a point in one second. The unit for frequency is waves per second or Hertz (Hz). One Hz = One wave per second. Wavelength and frequency are inversely related. The smaller the wavelength, the more times it will pass through a point in one second. The larger the wavelength, the fewer times it will pass through a point in one second.

The amplitude of a transverse wave is determined by the height of the crest or depth of the trough

http://www.stmary.ws/highschool/physics/home/animations3/waves/Wave_Characteristics.html

What are examples of transverse waves?

Example of a transverse wave:

strings on a musical instrument (not the sound) waves on a rope some waves in a spring some seismic waves (earthquake waves- secondary waves, to be exact)

What are Seismic Waves? An energy wave which vibrates through the earth’s crust as the crust bends or breaks. Seismic waves exist as both transverse and longitudinal waves. Some travel through the earth and some travel across the earth’s surface.

Electromagnetic waves are transverse waves that can travel without a medium through empty space. Examples: Radio Waves, Microwaves, Infrared, Visible Light, Ultraviolet, X-rays, Gamma Rays

http://www. stmary. ws/highschool/physics/home/animations3/wavemotion http://www.stmary.ws/highschool/physics/home/animations3/wavemotion.html

Light is an example of a transverse wave. Properties of Light Light is an example of a transverse wave.

Visible Light Waves Waves with a length of between 0. 4 and 0 Visible Light Waves Waves with a length of between 0.4 and 0.7 micrometers can be detected by the human eye. For these reason we call these waves visible light. As you look around the room everything you see has these waves bouncing off of them. If they didn’t, you would not be able to see them. What your eyes pickup and turn into a picture in your brain, are these visible light waves

Fun with light…

Light travels VERY FAST – around 300,000 kilometres per second. At this speed it can go around the world 8 times in one second.

Light travels much faster than sound. For example: Thunder and lightning start at the same time, but we will see the lightning first. 2) When a starting pistol is fired we see the smoke first and then hear the bang.

We see things because they reflect light into our eyes: Homework

Shadows Shadows are places where light is “blocked”: Rays of light

The colors of the rainbow: Red Orange Yellow Green Blue Indigo Violet

Adding colors White light can be split up to make separate colors. These colors can be added together again. The primary colors of light are red, blue and green: Adding blue and red makes magenta (purple) Adding blue and green makes cyan (light blue) Adding red and green makes yellow Adding all three makes white again

Only red light is reflected Seeing color The color an object appears depends on the colors of light it reflects. For example, a red book only reflects red light: Homework White light Only red light is reflected

A white hat would reflect all seven colors: A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and blue): Purple light A white hat would reflect all seven colors: White light

Using colored light If we look at a colored object in colored light we see something different. For example, consider this shirt and pair of shorts: Shirt looks red White light Shorts look blue

In different colors of light it would look different: Red light Shirt looks red Shorts look black Shirt looks black Blue light Shorts look blue

Some further examples: Object Color of light Color object seems to be Red socks Red Blue Black Green Blue teddy Green camel Magenta book Homework

Using filters Red Filter Filters can be used to absorb or “block” out different colors of light: Red Filter Magenta Filter

Investigating filters Color of filter Colors that could be “seen” Red Green Blue Cyan Magenta Yellow

Red Blue Green White Yellow Cyan Magenta

The Behavior of Waves What is reflection? When a wave bounces off an object and changes direction – this is reflection.

Reflection Reflection from a mirror: Mirror Normal Angle of incidence Incident ray Reflected ray Angle of incidence Angle of reflection Mirror

Angle of incidence = Angle of reflection The Law of Reflection Angle of incidence = Angle of reflection In other words, light gets reflected from a surface at ____ _____ angle it hits. The same !!!

What is sonar? Sonar is a system that uses the reflection of underwater sound waves to detect objects. This has been used to find sunken ships and schools of fish.

What is Refraction? Refraction is the bending of a wave as it passes from one medium to another. A wave travels at different speeds in different things. When a wave traveling a certain speed moves into another medium, it will either increase in speed or decrease in speed, resulting in a change in direction.

What is diffraction? Diffraction occurs when an object causes a wave to change direction and bend around it.

Diffraction also occurs when passing through a small opening Diffraction also occurs when passing through a small opening. They diffract and spread out as they pass through the hole.

What is Wave Interference What is Wave Interference? Waves interfere in one of two ways: Constructive Interference and Destructive Interference. Constructive Destructive

Extra Fun…

How is frequency related to pitch? The pitch of a sound wave is directly related to frequency. A high-pitched sound has a high frequency (a screaming girl). A low-pitched sound has a low frequency (a fog-horn). A healthy human ear can hear frequencies in the range of 20 Hz to 20,000 Hz. Humans cannot hear below 20 Hz. Sounds below this frequency are termed infrasonic. Sounds above 20,000 Hz are termed ultrasonic. Some animals, such as dogs, can hear frequencies in this range in which humans cannot hear.

Sound – The basics of frequency and pitch. We hear things when they vibrate. If something vibrates with a high frequency (vibrates very quickly) we say it has a high pitch. If something vibrates with a low frequency (vibrates slowly) we say it has a low pitch.

Drawing sounds… This sound wave has a _____ frequency:

Drawing sounds… This sound wave has a _____ amplitude (loud): This sound wave has a _____ amplitude (quiet):

http://www.stmary.ws/highschool/physics/home/animations3/waves/wave_measure.html

Other sound effects… Like light, sound can be… Reflected – sound reflections are called ______. Refracted – this is why you might sound strange if you try talking underwater

Loudness in Decibels

What is the Doppler Effect? The Doppler Effect is the apparent change in frequency detected when the sound is moving relative to the hearer. http://www.stmary.ws/highschool/physics/home/animations3/waves/DopplerEffectTrain.html

Using Sound: What is Acoustics? Acoustics is the study of sound and ways to optimize the hearing of sound inside various structures.

What is echolocation?