7 th grade Notes Week 17 Monday Waves

7 th grade Notes Week 17 Monday Waves Intro

Waves Intro: what it is… C-notes A wave is a disturbance caused by a force Example: you drop a pebble in water, a wave is formed

Waves: What do they do? C-notes Waves transfer ENERGY The molecules of the MEDIUM do NOT Move to another place…

Waves Intro: Causes & Examples C-notes a)Water waves…caused by wind (some by Earthquakes- tsunami) b)Ground shakes because pressure is released (EARTHQUAKE) c)You hit something it vibrates making a sound. Sound moves in waves

Waves Intro: Types of waves C-notes There are two types of waves: Mechanical and Electromagnetic

Waves Intro: Mechanical C-notes Mechanical waves are waves that move in MATTER. If there is no “MATTER”; there is no movement MEDIUM- is any type of matter that mechanical waves move in

Mechanical Wave: An example C-notes • Sound is an example of a mechanical wave. • Sound is produced by vibrations • The energy from the vibration moves in waves • Sound can ONLY travel if there is a medium

Waves Intro: Electromagnetic C-notes Electromagnetic waves can move through “empty” space. A place with little or no molecules is called a vacuum

Parts of a Transverse wave C-notes Crest- highest point of the wave REST LINE If there were no energy… Trough (troff)lowest point of the wave

Types of mechanical waves C-notes Transverse waves are waves in which the movement of the vibrating particles is perpendicular to the direction of the wave. Example: Water wave

Types of mechanical waves C-notes Longitudinal waves are waves in which the movement of the vibrating particles is parallel to the direction of the wave. Example: sound wave

Frequency: How many crests pass in a second Amplitude: Measure from rest line to crest Wavelength: Measure from one crest to the next Properties of (ALL) Waves

The energy of the wave. The more amplitude the more energy. The distance between one crest and another The number of vibrations (waves) each second. Unit used: hertz

Sound Energy C-notes Sound energy is the energy of vibration Sound produces an mechanical wave- it needs a medium to move in

Sound Energy C-notes Sound waves are LONGITUDINAL waves Another name for longitudinal waves is a COMPRESSION wave

Sound Energy C-notes Sound waves have the same properties as waves (amplitude, wavelength, frequency) However there are two “parts” to a COMPRESSION wave

Sound Energy C-notes Compression- where molecules of medium and pressed together Rarefaction- where molecules of a medium spread apart

Hearing and Wave properties C-notes Our ears can sense the amplitude of a sound wave The more energy, the more amplitude.

Hearing and Wave properties C-notes The greater amplitude is sensed as INTENSITY (LOUDNESS) The sound intensity is measured with a unit called decibel

Hearing and Wave properties C-notes Our ears can sense frequency of the vibration The more vibrations, the higher the frequency. This is a high pitch sound

Hearing and Wave properties C-notes Our ears can sense frequency of the vibration The more vibrations, the higher the frequency. This is a high pitch sound

Hearing and Wave properties C-notes Frequency is measured in a unit called HERTZ (Hz). These are vibrations per second We can “hear” 20 hertz to 20, 000 hertz