Waves

Waves

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What is a wave?

It is a repeating disturbance.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.



What is a wave?

It is a repeating disturbance.

Mechanical Waves

Waves that need a medium (stuff) to pass through.

Waves can only exist, if there is energy to transfer.

Solid ~ earthquake

Liquid ~ Tsunami

Gas ~ sound

Plasma ~ interstellar movements

Electromagnetic

Do NOT need a medium to travel through.

This is going to be any of the forms of light.


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Water waves are BOTH, compressional and transverse.

“According to a Japanese folktale, a venerable grandfather who owned a rice field at the top of a hill felt the sharp jolt of an Earth tremor one day just before the harvest. From his hilltop vantage point, he saw the sea pull back from the shore. Curious villagers rushed out to explore the exposed tidal flats and collect shellfish. From experience, the old man knew of the grave danger to his neighbors. With his grandson by his side, he dashed about his fields, setting fire to his crop. The villagers saw the smoke, and hurried up the hill to aid their neighbor. As they beat out the flames, they saw the old man scurrying ahead, setting new fires near the hill’s crest. Hoping to prevent him from destroying all of his crops, they rushed up the hill to stop him. Moments later, the villagers saw a tremendous wall of water surging onshore, flooding the flats where they had just been standing and they understood that the old man had sacrificed his harvest to save their lives.”

Transverse wave ~ wave goes at right angles to the direction of the wave itself.

a. All electromagnetic waves are transverse

b. Not all transverse wave are electromagnetic.

Compressional waves~

A wave that moves along the same direction as the medium of movement.

Earthquakes have both





Waves are defined by five things.

1. Wave height

2. Amplitude

3. Wavelength

4. Crest

5. Trough


are needed to see this picture.Wave height

Trough

Crest

Calculating Wave Speed

OK, this is not brutal, just a bit confusing.

velocity = wavelength • frequency

velocity is m/s

wavelength is m

frequency is Hz (cycles per second). Hz is the SI unit of frequency.

Calculating Wave Speed

OK, this is not brutal, just a bit confusing.

velocity = wavelength • frequency

velocity is m/s

wavelength is m

frequency is Hz (cycles per second). Hz is the SI unit of frequency.

Velocity is 5 meters • 100 cycle = 500 meters • cycles

cycle second cycles • second

If a wave is moving at 30 m/s

If it has a frequency of 10 Hz

What is its wavelength?velocity = wavelength • frequency

If a wave is moving at 300,000,000 m/s (light speed)

If it has a frequency of 1,400,000 Hz (KLIN radio)





300,000,000 m/s = (wavelength) • 1,400,000 Hz




300,000,000 m/s = (wavelength) • 1,400,000 Hz

So…(wavelength) = 300,000,000 ÷ 1,400,000




300,000,000 m/s = (wavelength) • 1,400,000 Hz

So…(wavelength) = 300,000,000 ÷ 1,400,000

So…….. A radio wave from KLIN radio is 214 meters long, about as long as two football fields.

Waves

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