Do Now: 4/16

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# Do Now: 4/16 - PowerPoint PPT Presentation

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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Presentation Transcript
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

4/6/11

Sound waves
• Sound wave: a mechanical wave transmitted through matter (a material medium)
Sound Waves:
• Sound is a longitudinal wave:
Pressure Variations
• Compression: particles closer together
• Rarefaction: particles farther apart
Properties of Sound: Pitch
• Pitch: The sensation of a frequency

Higher pitch! 

Music

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

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
• Amplitude represents energy
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
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:

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

v = 331 m/s + (0.6 m/s/C)•T

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

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:
• 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:
• Which property of sound is determined by amplitude?
• Which property of sound is determined by frequency?
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:
• 4th Q Project
• Homework questions
• Extra credit (optional)
Fourth quarter project