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Do Now: 4/16. A radio wave broadcasts at 700 kHz and travels the speed of light (3x10 8 m/s). 1.What is the period? 2.What is the wavelength?. Properties of Sound. 4/6/11. Sound waves. Sound wave: a mechanical wave transmitted through matter (a material medium ). Sound Waves:.

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Do now 4 16

Do Now: 4/16

A radio wave broadcasts at 700 kHz and travels the speed of light (3x108m/s).

1.What is the period?

2.What is the wavelength?


Properties of sound

Properties of Sound

4/6/11


Sound waves

Sound waves

  • Sound wave: a mechanical wave transmitted through matter (a material medium)


Sound waves1

Sound Waves:

  • Sound is a longitudinal wave:


Pressure variations

Pressure Variations

  • Compression: particles closer together

  • Rarefaction: particles farther apart


Properties of sound pitch

Properties of Sound: Pitch

  • Pitch: The sensation of a frequency

Higher pitch! 


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  • http://www.physicsclassroom.com/class/sound/U11l2a.cfm


Music

Music

Consonant: Certain sound waves which, when played simultaneously, will produce a pleasant sound


Example

Example:

Two musical notes that have a frequency ratio of 2:1 are said to be separated by an octave. A musical note that is separated by an octave from middle C (256 Hz) has a frequency of _____.

a. 128 Hz

b. 254 Hz

c. 258 Hz

d. 345 Hz

e. none of these


Review amplitude

Review: Amplitude

  • Amplitude represents energy


Properties of sound loudness

Properties of Sound: Loudness

  • Loudness depends on the amplitude of sound waves; measured in decibels (dB)

  • Intensity (I): how loud a sound is in relation to another


Example1

Example:

A mosquito's buzz is often rated with a decibel rating of 40 dB. Normal conversation is often rated at 60 dB. How many times more intense is normal conversation compared to a mosquito's buzz?

a. 2

b. 20

c. 100

d. 200

e. 400


Speed of sound

Speed of Sound:

The speed of sound depends primarily on medium but also on temperature:

v = 331 m/s + (0.6 m/s/C)•T


Example2

Example:

Determine the speed of a sound wave in air at a temperature of 20ºC.

v = 331 m/s + (0.6 m/s/C)•T

v = 331 m/s + (0.6m/s/C)•(20 C)

v = 331 m/s + 12 m/s

v = 343 m/s


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Echo:

  • echo: a reflected sound; will take twice the time to travel the same distance

  • Example: a sound wave travels 500 m to a cliff, then returns to where it started. If the sound wave traveled 330 m/s, how long does it take the sound to return to where it started?


Practice

Practice:

  • Use the rest of class to work on the worksheet “Sound Waves.”

  • Be prepared to answer an exit question at the end of class


Exit question

Exit Question:

  • Which property of sound is determined by amplitude?

  • Which property of sound is determined by frequency?


Do now 4 17 12

Do Now (4/17/12):

  • Which property of sound is determined by amplitude?

  • Which property of sound is determined by frequency?

  • What is the velocity of sound when the temperature is 44˚ C?


Agenda

Agenda:

  • 4th Q Project

  • Homework questions

  • Extra credit (optional)


Fourth quarter project

Fourth quarter project

  • Deadline 1: TOMORROW

    Bring in your favorite piece of art, or any art piece that speaks to you. It can be a drawing, a painting, a sculpture, etc. You may make a photocopy, or print it from a computer, but you MUST have a hard copy with you… on your phone doesn’t count!!!

    You will also write a paragraph about your piece, but we will do that tomorrow.


Practice1

Practice:

  • Work on homework

  • Work on extra credit (optional) – if you want extra credit, the work must be submitted by the end of class

  • Begin thinking about your art piece – feel free to look through your history or English textbook once you have finished your work.


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