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How do waves move?. Compare solid liquid & gas Solid faster than liquid faster than gas (needs medium) More dense – faster What about light? Fastest in vacuum (no medium) More dense - slower.

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How do waves move
How do waves move?

  • Compare solid liquid & gas

    • Solid faster than liquid faster than gas (needs medium)

    • More dense – faster

  • What about light?

    • Fastest in vacuum (no medium)

    • More dense - slower


Sound wave

Sounds that are too high in frequency for humans to hear are called ultrasound. Normally, these sounds are above 20,000 Hz.

Sounds that are too low in frequency for humans to hear are called infrasound. Normally, these sounds are below 20 Hz.

Sound Wave


Doppler effect
Doppler effect called ultrasound. Normally, these sounds are above 20,000 Hz.

  • Apparent change in pitch of a sound caused by the motion of object making sound


Infrasound called ultrasound. Normally, these sounds are above 20,000 Hz.

Infrasound is sound with a frequency too low to be heard by the human ear. The study of such sound waves covers sounds beneath the lowest limits of human hearing (20 hertz). Many animals, including whales, elephants, rhinoceros, giraffes, okapi, and alligators, communicate using infrasound.Used in movies to give a feeling of unease; can vibrate your whole body


Interference
INTERFERENCE called ultrasound. Normally, these sounds are above 20,000 Hz.

When two or more waves come together, they “superimpose” or add together. The total amplitude is simply the sum (positive & negative!) of all the individual amplitudes. The extremes of what can happen are called constructive interference and destructive interference


What is this called
What is this called? called ultrasound. Normally, these sounds are above 20,000 Hz.

Constructive interference

Destructive interference


What is this called1
What is this called? called ultrasound. Normally, these sounds are above 20,000 Hz.

Destructive interference


Standing wave
Standing Wave called ultrasound. Normally, these sounds are above 20,000 Hz.

waves generated when a series of wave pulses are sent through a medium and then reflected back upon themselves.

Nodes – distructive interference

Antinodes – constructive interference


Refraction
Refraction called ultrasound. Normally, these sounds are above 20,000 Hz.

  • Occurs as waves move from one medium into another or within a medium, like air, that varies  in density or temperature


Spearfishing
Spearfishing called ultrasound. Normally, these sounds are above 20,000 Hz.


Refraction1
Refraction called ultrasound. Normally, these sounds are above 20,000 Hz.

Incedent ray

ϴi

ϴi

ϴr

Emergent ray

ϴr


Reflection from plane mirror
Reflection from Plane Mirror called ultrasound. Normally, these sounds are above 20,000 Hz.


Problems
Problems called ultrasound. Normally, these sounds are above 20,000 Hz.

  • v = d / t speed = distance / time The unit for speed (or velocity) (v) is meter/second.The unit for distance (d) is meter.The unit for time (t) is second. v = 331 m/sec + (0.6 m/s/C)  Tspeed of sound in air = 331 m/sec + (0.6)(room temperature)The unit for speed (or velocity) (v) is meter / second.

  • The unit for room temperature (T) is degrees Celsius.

  • v = f 

  • speed = frequency times wavelength

  • The unit for speed (or velocity) (v) is meter/second. The unit for frequency (f) is Hertz (Hz).

  • The unit for wavelength () is the meter.


Calculate the speed of sound for the following temperatures
Calculate the speed of sound for the following temperatures. called ultrasound. Normally, these sounds are above 20,000 Hz.

  • 0 C (cold day)

  • 35 C (hot day)

  • 100C


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