amplitude wave and sound wave

Observer receding from the source wave sound

2006-10-28T20:49:00.000-07:00

Observer receding rom the source Again, suppose that the bank alarm is emitting sound at a frequency of 500Hz. As we drive away from the bank at 22 m/s, what is the frequency that we hear? In this case, the wavelength is still the same as we computed in the case above, 0.686m. The bank is not moving, so the waves are neither compressed nor spread out. The velocity of the waves relative to the car is different, however. Since the car is moving away from the bank, it is as if the car is trying to outrun the sound waves coming from behind. The relative velocity, therefore, will be the speed of sound minus the speed of the car:
v' = 343 - 22 = 321 m/s
Lastly, we use these numbers to calculate the observed velocity:
f' = v' / L' = 321 / 0.686 = 468 Hz
When the observer is receding from the source, he or she hears a lower frequency than normal. Summary If the source of sound is moving, we will have a different wavelength than normal. It will be less than normal if the source is approaching and greater than normal if the source is receding. The amount that it will be greater or less by is always the distance that the source travels during one period. A moving source does not affect the velocity of the sound waves. If the observer is moving, the sound will appear to be moving at a different velocity relative to the observer. The velocity of sound for the moving observer will be 343 m/s plus the speed of the observer if the observer is approaching the source and 343 m/s minus the speed of the observer if the observer is receding. The motion of the observer does not affect the wavelength. If both the source and the observer are moving, then there will be both a different wavelength and a different velocity. Once the new wavelength and the new velocity are know, the velocity is divided by the wavelength to give the observed frequency.

Calculations for the Doppler Effect with a Movin Observer

2006-10-27T01:39:00.000-07:00

We will now consider the above case in the form of a specific problem. We are once again given an original frequency emitted by some source of sound and told to calculate the observed frequency. Observer approaching the source Suppose the bank alarm is emitting a sound at a frequency of 500Hz and we are driving toward it at 22 m/s. What is the frequency that we hear? Once again, we are looking for the observed frequency, f . We will again use our equation:
f' = v'/L'
All we have to do is find v'and L' and we can get our answer. Both are pretty easy to find. Since the car is moving into the sound waves, the velocity of the waves relative to the car will be greater. We simply add the velocity of the car to the speed of sound:
v' = 343 + 22 = 365 m/s
Because the bank is not moving, the sound waves will not be bunched up or spread out. The observed wavelength, L', will be the same as the original wavelength L . We can find this from the given information in the problem:
L' = L = v/f = 343/500 = 0.686m
We use these two numbers, v' and L' , to find the observed frequency:
f' = v'/L' = 365/0.686 = 532 Hz
So we see that when the observer is approaching the source, he or she hears a higher frequency than when still. If that example made sense to you, it should now be easy understand the next case.

The doppler effect w

2006-10-26T06:29:00.000-07:00

We have seen that the Doppler effect occurs whenever the source of a sound is in motion. Now we will see that the Doppler effect is also observable as a result of the motion of the listener, even if the source of sound is stationary. To explain this, we imagine ourselves to be driving past an object that is making a loud, steady noise. Pretend that we are driving past a bank that has just been robbed. The bank's alarm is on. Imagine that the alarm is quite loud, and that we can hear it well as we approach the bank and as we drive past and head away from it. The bank is obviously stationary. The sound waves therefore all originate from the same point and expand outward in perfect symmetry. There is no bunching of the wave fronts on one side as there was when the train went past. The waves are equidistant from each other on all sides. In this case, however, we are first headed into the wave fronts. As we approach the bank, we are headed directly into the waves and the waves are likewise headed directly into us. Because of this "head on collision", the waves are, from our point of view, moving past us at a greater speed than if we were sitting still. Because they are passing us faster, more of them go by us each second. We therefore hear a higher frequency sound as we drive into the waves. Note that the waves are always moving at the speed of sound, 343 m/s. It is their velocity relative to us that has changed because of our motion. As we drive away from the bank, the waves are overtaking us from behind. Because we are moving along in the same direction as the waves, they do not pass us as quickly as they would if we were still. Since they do not pass us as quickly, fewer of them go past us each second. Fewer waves per second is, by definition, lower frequency. Therefore, as we drive away from the bank we hear a lower frequency. It should now be realized that the Doppler effect can be observed as a result of motion. This motion can be motion of the source of the sound, motion of the observer, or a combination of both.

wavelength to calculate

2006-10-24T23:46:00.000-07:00

Behind the train: From this point it is easy to figure out what frequency a person would hear behind the train, after the train had passed. Behind the train, the waves are more spread out. After the first wave is emitted, the train moves a distance of 0.08 meters before the next wave is emitted. The wavelength is therefore increased by this amount.
L' = L + x = 1.372m + 0.08m = 1.452m
This is the observed wavelength which we use to calculate the observed frequency.
f' = v'/L' = 343/1.452 = 236 Hz
Behind the train, a person would hear a frequency of 236 Hz, slightly lower than the original 250 Hz emitted by the train's whistle.

The second wave front

2006-10-23T22:49:00.000-07:00

In front of the train:The second wave front, however, is not emitted from the same place because the train is moving forward. After the first wave is emitted, the train has 1/250 s to travel forward before the second wave appears. How far does the train travel during this time? Again, we can use the formula for distance to calculate how far the train has moved.
x = vt = 20 * (1/250) = 0.08m
In other words, the second wave front is 0.08m closer to the first than if the train were still. The new wavelength L' is therefore 0.08m shorter than the original wavelength L.
L' = L - x = 1.372m - 0.08m = 1.292m
This new wavelength, 1.292m, is the wavelength the observer in front of the train actually hears.This is he
wavelength we will use to calculate the observed frequency. Our equation will be
f' = v'/L'
The velocity, v', in the above equation is the same as v. It is 343 m/s. The sound waves move through the air at 343 m/s regardless of the motion of the train. Our final calculation is therefore
f' = v'/L' = 343/1.292 = 265 Hz
The observer hears a frequency of 265 Hz, slightly higher than the original 250 Hz sound produced by the train.

Calculations Involving the Doppler Effect

2006-10-23T06:20:00.000-07:00

In this section we will explain how to solve problems that involve the Doppler effect. The math is not difficult. Rather than deriving an equation, we will go through the conceptual steps involved in solving a Doppler effect problem. At the end of this section, you should understand how to solve any Doppler effect problem involving a moving source, a moving observer, or both. In general, we want to calculate the observed frequency. Given the original frequency of the sound produced, we want to calculate the frequency that is actually observed, which is different due to the motion. We have to define our terms and variables with precision.
f = original frequency. The frequency of the sound coming from the source.
f' = observed frequency. The frequency that the observer hears. (pronounced "f primed")
L = original wavelength. The wavelength of the sound produced by the source if the source were still.
L' = observed wavelength. The actual wavelength that is observed. It will be either shorter or longer than the original wavelength due to the motion. (pronounced "Lambda primed")
v_source = velocity of the source of sound
v_observer = velocity of the observer
v_sound = velocity of sound. In air, this is 343 m/s.
v'sound = velocity of sound that is actually observed. This will be either greater or less than 343m/s if the observer is moving. We will also use a few simple equations:
v = fL v' = f'L' x = vt
To begin, we will consider the following simple case: Suppose you are standing beside the railroad tracks as a train is approaching. The train blows its whistle, which emits a sound at a frequency of 250 Hz. If the train is moving toward you at 20m/s, what is the frequency that you hear? After the train passes you and heads away form you, what is the frequency that you hear? To solve this problem, try to picture in your mind the sound waves being emitted from the train whistle. We know the velocity of sound, 343 m/s, and we know the frequency of the waves, 250 Hz. From this we can calculate the wavelength:
L = v/f = 343/250 = 1.372m
This would be the wavelength of the waves if the train were not moving. The train is, however, moving forward, and the waves in front of the train are closer together. The question is: How much closer together are they? We need to find L' , the actual wavelength the observer sees. The waves are being emitted at a frequency of 250 Hz. This means that every 1/250 of a second, a wave front is emitted. This time, 1/250 s, is the period. After one wave is emitted, it travels forward for 1/250 s before the next wave appears. How far does the wave travel in this time? We can compute the distance the wave travels using a simple formula: distance = velocity x time.
x = vt = 343 * (1/250) = 1.372m
The answer we get is 1.372m, precisely one wavelength,which is exactly what we would expect. Each wave travels one wavelength before the next wave is emitted.

THE DOPPLER EFFECT EXPLAINED

2006-10-22T09:25:00.000-07:00

To explain the Doppler effect in detail, we will use the example of a train passing.
Let us imagine that a train passes us as we stand next to the railroad tracks, and let us imagine that as it approaches us, there is a long steady blow of the train's whistle. As the whistle blows, sound waves are emitted from the whistle at a constant frequency. If the train were still, the frequency of the waves emitted from the whistle would be the exact frequency that we would hear. Because of the motion of the train, however, this is not the case. Picture in your mind the sound waves being emitted from the train whistle and expanding outward as ever enlarging spheres. When the first wave is emitted, it begins to expand from the point at which it was emitted. Before the second wave is emitted, though, the train has moved forward some. The second wave is then emitted and begins to expand outward. Because of the motion of the train between the two wave emissions, the second wave will be closer to the first wave on the front side of the train, and farther from the first wave on the back side of the train. The train will then move forward some more before the third wave is emitted. Each wave that is emitted ends up being closer to the previous wave on the front side of the train and farther from the previous wave on the back side of the train. In front of the train, the wave fronts are bunched together; behind the train, the motion has spread them out. Now imagine these waves coming toward us as we listen. The waves in front of the train are closer together than they would be if the train were still. They are,however, still moving at normal speed, 343 m/s. Because they are closer together, more of them pass us each second. Saying that more of them pass us each second is equivalent to saying that they pass us at a higher frequency. We therefore hear a higher pitch. After the train passes us, we are then behind it,where the sound waves are spread farther apart. As before, the waves are still moving at 343 m/s. Because they are farther apart, not as many of them pass us each second. We therefore hear a lower frequency sound behind the train. This is our common experience with the Doppler effect.Moving objects seem to produce a higher pitch sound as they approach and a lower pitch sound as they recede.

VELOCITY AND WAVELENGTH

2006-10-19T20:52:00.000-07:00

Two other characteristics of waves are important: the velocity and wavelength.The velocity of a wave is simply how fast the wave moves,and is commonly measured in meters per second (m/s).Sound waves propagate through the air at approximately 343 m/s,or about 767 miles per hour.At this peed, the sound waves travel one mile in about five seconds.While the speed of sound is generally considered constant,it is not a truly constant value.The actual velocity varies slightly depending on the temperature and the density of the air.Sound will therefore travel at different speeds at different altitudes and in different atmosphericconditions. For practical purposes,however,343 m/s is an accurate value for the speed of sound waves that we hear in everyday life,and we can consider this value to be constant.The letter 'v' is commonly used to denote velocity.Waves are often modelled mathematically by the sine function. It may be easy to see why.Many waves that we see in real life take on the shape of a sine curve.Waves on the surface of water,for instance,or waves travelling down a rope generally have a shape that is very similar to the sine function.Sound waves,because of their nature, do not have this specific shape,but they can still be modelled by a sine curve.Picture a sound wave, as in the diagram,with a sine curve drawn next to it.The regions of compression could correspond to the peaks of the sine wave and the rarefactions could correspond to the troughs. Mathematically,this comparison is perfectly valid,and allows sound waves to be dealt with mathematically using the sine function.The wavelength is the distance between two individual wave fronts.For waves on the surface of a pond, the wavelength is easy to see.It is simply the distance between two peaks,or the distance between two troughs.For a sound wave,the wavelength is the distance between two compressions, which is the same as the distance between two rarefactions.Wavelength is commonly measured in meters.Wavelength is directly related to frequency.If sound waves are being produced at a very high frequency, each wave will not have time to travel very far before the next one is emitted right behind it.The wavelength will consequently be relatively short.In general,the higher the frequency,the shorter the wavelength.The reverse is also true:lower frequency waves have larger wavelengths.The Greek letter "lambda",is commonly used to denote wavelength.Mathematically,the relationship between velocity,frequency, and wavelength is given by the equation velocity = frequency x wavelength Higher frequency sounds, therefore, have a shorter wavelength.If the wavelength is short, then the individual wave fronts must be close together.Since they are close together,many of them strike your ear in a given second, and you hear a high frequency.

The unit for period Hertz.

2006-10-18T21:08:00.000-07:00

The frequency of a wave is the number of wave fronts passing a given point per unit time. There is another quantity that is closely related to this: the period.the period of a wave is the time between each wave emission.If you are standing still watching waves go past on the surface of a lake,the period of the waves would be the time it took for one entire wave pulse to completely pass.Period is related to frequency in an obvious fashion - the higher the frequency,the smaller the period.If there are alot of waves going by each second,then clearly the time between each wave is very small.The symbol for period is the letter "T" and it is commonly measured in seconds.The inverse relationship between period and frequency is expressed in the following equation:

T = 1/f or f = 1/T

The unit for period,seconds,is the inverse of the unit for frequency, Hertz.

The frequency of a sound wave

2006-10-17T22:24:00.000-07:00

Imagine once again a guitar string that has been plucked and is vibrating back and forth.The string will be oscillating at a certain frequency,that is, it will vibrate back and forth a certain number of times per second,producing a new wave each time.'Frequency' is defined here as the number of oscillations per second.A high frequency vibration produces high frequency sound waves.An object vibrating more slowly produces lower frequency sound waves.Frequency is measured in 'Hertz'.One Hertz is simply one oscillation per second.A guitar string vibrating back and forth 150 times each second is said to be vibrating at 150 Hertz (abbreviated '150Hz').The letter 'f'is commonly used to denote frequency.The frequency of a sound wave determines the pitch (the particular note) that we hear. A high frequency sound wave is heard by the human ear as a high pitch,or a high note, while a low frequency wave is heard as a low pitched sound.This relationship between frequency and pitch is actually readily observable by the human eye.If you look inside a piano or look carefully at a guitar while it is played, you will be able to see that the larger,fatter strings vibrate more slowly.These low frequency oscillations produce the low notes.The small,thin strings vibrate much more rapidly and produce the high notes.These waves travel through the air from the instrument to the listener's ear.Note that there is not any mass of air that travels from the source to the listener's ear;it is simply the disturbance of the air that travels.These waves enter our ears, causing the ear drum to vibrate, producing the sensation of hearing. Just as the sound waves are produced at a certain frequency,they enter the ear at a certain frequency.If you are listening to a guitar string that has been plucked,the frequency at which the string oscillates will be the same as the frequency of the sound wave that enters your ear,and you will hear the corresponding note.A vibration of about 256 Hz produces the note Middle C.A vibration at twice this frequency will produce a note exactly one octave higher.A vibration of about 440 Hz will produce the note A. A vibration of 880 Hz will produce an A one octavehigher.In general,doubling the frequency of the vibration increases the pitch by one octave.The human hear can detect sounds within a certain requency range.The lowest sound a human can hear is around 20 Hz.The highest sound the ear can detect is usually around 20,000 Hz.The upper limit,however,usually decreases as a person ages.While young people can hear sounds as high as 20,000 Hz,older people may only be able to hear sounds as high as 15,000 or even 10,000 Hz.Some animals can hear sounds that are out of the range of human hearing.Dogs and bats,for example,can hear ultrasonic sounds, sounds to high for the human ear to detect.Some birds are believed to be able to hear infrasonic sounds,which are below the range of human hearing.

To understand the Doppler effect

2006-10-15T21:14:00.000-07:00

understand the Doppler effect,one must first know something about sound waves.Sound waves are a part of our everyday experience because everything we hear is a sound wave.These waves are produced by objects that are moving or vibrating.The wave itself is simply a disturbance in the air caused by the vibrating object. As an example, consider a simple tuning fork:a tuning fork is designed to vibrate back and forth a certain number of times each second. With each vibration, a sound wave is produced.This is because the tuning fork pushes on the air molecules around it as it moves.When a prong of the fork vibrates forward,it pushes on the air in front of it,forming a small region of compressed air.This compressed air naturally tries to expand.As it expands,it pushes on the air next to it,causing it to compress.This new compressed region then acts on the air next to it,and the process continues so that the compression travels through the air.Meanwhile,the prong of the tuning fork vibrates back in the opposite direction,forming a region of expanded or rarefied air. This rarefaction is a region of low pressure,and the air nearby rushes into it.The rarefaction also travels through the air just as the compression did.As the tuning fork continues to vibrate,alternating regions of compression and expansion travel through the air.This disturbance propagating air disturbance is a sound wave. Not all of us use tuning forks every day,but most of us are familiar with musical instruments and the sound waves they produce.A guitar string is a good example: When a guitar string is plucked,it vibrates back and forth,causing the air molecules next to the string to vibrate back and forth. These vibrating air molecules then bump into adjacent molecules, causing them to vibrate.The disturbance spreads as these molecules in turn vibrate the ones next to them.This disturbance is the sound wave,and one single disturbance is known as a wave front.If unhindered,the wave front spreads outward from the source in an ever expanding sphere,weakening in intensity as it enlarges.With each back and forth motion of the guitar sting, a new wave front is produced and spreads outward,following the one before it. When you speak,vocal chords vibrating in your throat produce sound waves in the same manner as a vibrating guitar string or tuning fork.

INTRODUCTION TO SOUND WAVES

2006-10-14T18:27:00.000-07:00

When a fast-moving object such as a car or a motorcycle or a train passes by, we notice a change in the pitch of the sound coming from the object.As the object approaches us, we hear a higher frequency sound. After the object passes us and travels away,it seems to be emitting a lower frequency sound.This apparent change in frequency is known as the Doppler effect.The Doppler effect only occurs when objects move.Furthermore,the objects need to be moving relatively fast.We do not notice a change in the pitch of a person's voice as he or she walks past us, but we do notice the change in pitch of a motorcycle engine as it passes at highway speed.The Doppler effect, therefore, went largely unobserved before the invention of trains and automobiles capable of traveling at significant speeds. The concept was first correctly identified and explained by J. C. Doppler in 1842.

2006-10-12T19:13:00.000-07:00

WAVE:A disturbance that propagates through a medium. Waves can occur in any material. Light,or electromagnetic radiation,can travel in a vacuum and is the only example of a wave which requires no medium through which to travel. WAVE FRONT:One individual wave pulse,sometimes referred to as a single wave.When used in reference to sound waves,the term generally refers to a single compression region of the wave.
WAVELENGTH:The distance between two consecutive wave fronts.Wave length is commonly measured in meters and is directly related to the wave's frequency and velocity according to the equation v = f .
YEAGER,CHUCK:American test pilot.Chuck Yeager was the first person to fly faster than sound in the experimental aircraft known as the X-1.

SUPER SONIC

2006-10-10T17:33:00.000-07:00

SUBSONIC:Slower than the speed of sound.Any speed less than Mach 1 is referred to as subsonic.
SUPERSONIC:Faster than the speed of sound.Any speed greater than Mach 1 is referred to as supersonic.
ULTRASONIC:Above the frequency range of human hearing;above 20,000 Hz.
VELOCITY:The speed at which something is moving in a particular direction. Velocity is commonly measured in meters per second. Velocity is a vector quantity and always has a direction associated with it.

SOUND

2006-10-09T20:27:00.000-07:00

SOUND:The propagation of molecular vibrations through a material. Sound is generally associated with waves travelling through the air, but sound can travel through any material. Any longitudinal wave passing through a material can properly be referred to as a sound wave.
STEADY STATE THEORY: The theory that the universe exists in a steady state, unchanging. According to the steady state theory,the universe has always existed in its present condition. Although it enjoyed wide acceptance at one time,most scientists now believe that the universe has
not existed forever but had a beginning at a specific point in time known as the big bang. coming up

SONIC BOOM

2006-10-08T22:03:00.000-07:00

Hi,you can to continu.
SONIC BOOM:The loud noise associated with a shock wave. Sonic booms are commonly caused by supersonic aircraft.From a distance,the sonic boom sounds similar to thunder. At close range it can be physically damaging or deafening. Because of the inherent possibilities of damage or injury from a sonic boom, aircraft generally do not travel at speeds of Mach 1 or greater at low altitudes over populated areas. Bye to next time.

SHOCK WAVE

2006-10-07T17:34:00.000-07:00

Hi,Learn about post12 for you.
SHOCK WAVE:The large amplitude sound wave produced by an object travelling at Mach one or faster.When an object reaches the speed of sound,the sound waves it produces can no longer outrun it.The sound waves "pile up" in the front of the object and interfere constructively to
produce one extremely large sound wave. At Mach 1, this shock wave is in the front of the object. At speeds greater than Mach 1,the shock wave takes on the shape of a cone spreading out behind the object,similar to the wake behind a boat. Thanks so much to see next post.

The theory of relativity

2006-10-06T19:32:00.000-07:00

Hi,continued from post 10
RED SHIFT:The change in color toward the red end of the spectrum due to an object's motion away from an observer.The red shift is due to the Doppler effect.It is only noticeable when an object is moving extremely fast.
RELATIVITY:The common name for the theories put forth
by Albert Einstein in 1905 and 1915.The theory of relativity replaced Newtonian mechanics and revised common notions of space and time.The General Theory of Relativity predicted the expansion of the universe.Thanks

quality of a sound

2006-10-05T22:12:00.000-07:00

OCTAVE:A musical interval equivalent to doubling or halving the frequency of a given note.A note that is one octave higher will have twice the frequency;a note one octave lower will have half the frequency.
PERIOD:The time for one complete oscillation;the time for one complete wave front to pass;the time between wave emissions.Period is the inverse of frequency and is
commonly measured in seconds.
PITCH:The quality of a sound or musical note generally referred to as "high" or "low".A high pitched sound is produced by a high frequency vibration.A low pitched sound is produced by a low frequency vibration.On stringed instruments,high pitched sounds come from the shorter,smaller,and more tightly tuned strings.To next post.

NEWTONIAN PHYSICS

2006-10-03T23:52:00.000-07:00

Hi this 9 post to scientific.
NEWTONIAN PHYSICS:Also known as "Classical Physics." Newtonian physics consists of the theories of developed by Isaac Newton and those who came after him.In the late 1800's, many scientists were confident that
Newtonian physics would provide the final and nearly complete understanding of the world.After 1900, Newtonian physics was shown to be only a good approximation and was replaced by modern physics. Bye to see next post and thanks.

a multiple of the speed of sound

2006-09-29T07:49:00.000-07:00

Hi.This 8 posts for everyone.
MACH NUMBER:A number indicating speed as a multiple of the speed of sound.An object moving at Mach 1 would be moving at exactly the speed of sound.Mach 2 would be a speed twice that of sound,etc.
MACH,ERNST:(1838-1916).Austrian physicist and philosopher.
MEDIUM:The material through which a wave propagates.For sound waves that we hear,the medium is commonly air.Light,or electromagnetic radiation,is the only example of a wave that requires no medium through which to travel.
MODERN PHYSICS:Physics after the year 1900 is commonly known as modern physics.Based on Einstein's theories of relativity, and on the theories of quantum mechanics developed by Max Planck and Neils Bohr,modern physics replaces classical or Newtonian physics as a more current understanding of the world. bye to next post.

Infrasonic sounds

2006-09-22T20:14:00.000-07:00

Hi.This 7 post.
INFRASONIC:Below the frequency range of human hearing;below 20 Hz.Infrasonic sounds can be produced by thunder,earthquakes and heavy machinery.
INTERFERENCE:The superposition of two waves.When two or more waves meet each other, the waves combine and form a new wave.The amplitude of this new wave at any point will be the mathematical sum of the amplitudes of the original waves.
LOUDNESS:How loud a sound is as heard by the ear.The loudness of a sound wave is determined by the amplitude of the vibration.(Loudness is commonly referred to as
"volume",although this term is sometimes avoided in this context so that sound volume is not confused with spatial volume.)
Thank see you next post

Doppler effect in distant stars and galaxies.

2006-09-20T18:02:00.000-07:00

Hi,Be beck
HUBBLE,EDWIN:(1889-1953).American astronomer.Hubble's observation of the Doppler effect in distant stars and galaxies help form the foundation of modern understanding of cosmology.Hubble observed that distant galaxies and stars are red shifted and therefore must be moving away from us at very high speeds.These observations are direct evidence that the universe expanding.
HUBBLE'S LAW:A mathematical principle that states that the velocity at which a distant star or galaxy is receding from Earth is directly proportional to its distance.The relationship is expressed in the equation v = Hod where v is the velocity of recession,Ho is the Hubble constant,and is the distance of the receding object from Earth.The precise value of the Hubble constant is not known.
And to next 7 post,Thank you everyone.

Frequency unit of HERTZ

2006-09-19T19:14:00.000-07:00

Hi,To continue form DOPPLER EFFECT.
EINSTEIN,ALBERT:(1879-1955).German-born American physicist.Einstein produced the theories of Relativity in the early 1900's that form the basis of modern physics. These theories gave scientists a different understanding of space and time, and also predicted the expansion of the universe.
FREQUENCY:The number of oscillations per unit time. Frequency is commonly measured in oscillations per second, or Hertz.
GLOBAL POSITIONING SYSTEM:A network of satellites which circle the globe and broadcast radio signals.These signals are analyzed by GPS units on the ground to yield information about position and speed.
HERTZ:The unit of measurement for frequency.One Hertz, or 1 Hz, is defined as one oscillation per second.
HERTZ,HEINRICH:(1857-1894).German physicist.
To next post Thank You.

DOPPLER EFFECT

2006-09-19T03:38:00.000-07:00

Hi,my friends this fourth post for guy and i to be glad in feeling form everybody.
DESTRUCTIVE INTERFERENCE:When two waves occupy the same space at the same time,their amplitudes add.If they tend to cancel each other out in doing so,the waves are said to be interfering destructively.

DOPPLER EFFECT:The apparent change in frequency of a sound wave.The Doppler effect can be caused by the motion of the source of the sound,the motion of the observer,or by the motion of both.

DOPPLER,JOHANN CHRISTIAN:(1803-1853).Austrian physicist and mathematician. J.C.Doppler first explained the Doppler effect in 1842.

DOPPLER RADAR:Radar systems often utilize the Doppler effect to measure velocity. A light wave emitted atan object will be reflected back at a different frequency if the object is moving.The change in frequency can then be used to determine the velocity.
bye see you to next post.

larger amplitude wave

2006-09-18T14:52:00.000-07:00

To be continue.
BLUE SHIFT:The change in color toward the blue end of the spectrum due to an object's motion toward the observer.The blue shift is a result of the frequency of light waves coming from an object being affected by the Doppler effect.It is only noticeable when objects are moving at very high speeds.
CONSTRUCTIVE INTERFERENCE:When two waves occupy the same space at the same time,their amplitudes add.If they add to produce a wave with a larger amplitude,they are said to be interfering constructively. To be on post 4.

amplitude sound wave

2006-09-17T14:50:00.000-07:00

Hi,continued from post 1.
BIG BANG:The big bang theory teaches that at a specific moment,the universe began as a very small,extremely dense mass that exploded outward in a violent explosion.According to the theory, the universe is continuing to expand today as a result of this initial explosion.The observed red shift of distant stars and galaxies is one of the primary pieces of evidence for the big bang theory.Not end to be back to 3 posts.

amplitude wave

2006-09-16T14:48:00.000-07:00

amplitude wave

Hi. Welcome to my first post in glossry amplitude wave.And learn more sonic sound wave.

AMPLITUDE:The term 'amplitude' refers to the physical size of an oscillation.For sound waves in air,the amplitude is the maximum distance an individual air molecule will move from its starting point as a sound wave passes by. The amplitude of a sound wave determines its loudness. A sound wave with a large amplitude will sound louder than a small amplitude wave.
End post to be continue I'm think this post will be used for the benefit of everyone.