wave

[silverice]

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Increase the wave amplitude effects its intensity, but not its wavelength or frequency. I'm not comfortable with this concept, please help.

I always image waves are composed of millions of particles. So if we were to increase the amplitude, If were trace the wave from note to note, the distance would have increased. In order to have the same frequency the particles must travel faster, and therefore changing the wavelength. But another way is that more particles can come in and increase the intensity so that both wavelength and frequency can stay the same. I think of intensity as the number of particles in the wave pass through a particular point.

Am I right?

 

[milski]

Yes and no. You have to keep in mind that the particles are not moving with the wave. The particles are moving up and down, the wave propagates horizontally. If you left a floating object on the surface of water in which you are creating waves, the object will bob up and down but will not change positions horizontally. Do not confuse that with how waves break at a beach - in that case they do carry objects horizontally but that's not the type of waves that are discussed when talking about simple harmonic motions.

Once that is out of the way, you are correct that the particles will have to travel faster up and down to keep the frequency the same. That means that they have more kinetic energy and is the reason why the intensity will increase when the amplitude is increased. In your way of thinking, intensity is how much energy do the particles in a single section of the wave have. Saying that it's the number of particles passing through that point is incorrect because the particles will stay at that point indefinitely.

The speed at which the wave propagates is not related to its energy but to the media - it's determined from how fast the moving particles can make their neighboring particles to move in the same direction as themselves.

 

[MedPR]

Yes and no. You have to keep in mind that the particles are not moving with the wave. The particles are moving up and down, the wave propagates horizontally. If you left a floating object on the surface of water in which you are creating waves, the object will bob up and down but will not change positions horizontally. Do not confuse that with how waves break at a beach - in that case they do carry objects horizontally but that's not the type of waves that are discussed when talking about simple harmonic motions.

Once that is out of the way, you are correct that the particles will have to travel faster up and down to keep the frequency the same. That means that they have more kinetic energy and is the reason why the intensity will increase when the amplitude is increased. In your way of thinking, intensity is how much energy do the particles in a single section of the wave have. Saying that it's the number of particles passing through that point is incorrect because the particles will stay at that point indefinitely.

The speed at which the wave propagates is not related to its energy but to the media - it's determined from how fast the moving particles can make their neighboring particles to move in the same direction as themselves.

I'm still confused about this as well.

So one way to increase amplitude is to throw in more kinetic energy, correct? So increased kinetic energy means increased velocity.

If velocity = f*lambda, then doesn't increased velocity increase either (or both) lambda or frequency? And if increased velocity is necessary to increase KE, and KE is necessary to increase amplitude, then doesn't an increase in amplitude increase f and/or lambda?

 

[silverice]

Yes and no. You have to keep in mind that the particles are not moving with the wave. The particles are moving up and down, the wave propagates horizontally. If you left a floating object on the surface of water in which you are creating waves, the object will bob up and down but will not change positions horizontally. Do not confuse that with how waves break at a beach - in that case they do carry objects horizontally but that's not the type of waves that are discussed when talking about simple harmonic motions.

Once that is out of the way, you are correct that the particles will have to travel faster up and down to keep the frequency the same. That means that they have more kinetic energy and is the reason why the intensity will increase when the amplitude is increased. In your way of thinking, intensity is how much energy do the particles in a single section of the wave have. Saying that it's the number of particles passing through that point is incorrect because the particles will stay at that point indefinitely.

The speed at which the wave propagates is not related to its energy but to the media - it's determined from how fast the moving particles can make their neighboring particles to move in the same direction as themselves.

I'm doing the sound chapter now, I think I will understand better after that. I'll get back to this question. I realize that if I don't beat the concept or question to death I'll just end up getting the same question wrong. Sorry for being so meticulous.

 

[dsoz]

I'm still confused about this as well.

So one way to increase amplitude is to throw in more kinetic energy, correct? So increased kinetic energy means increased velocity.

If velocity = f*lambda, then doesn't increased velocity increase either (or both) lambda or frequency? And if increased velocity is necessary to increase KE, and KE is necessary to increase amplitude, then doesn't an increase in amplitude increase f and/or lambda?

Don''t confuse the speed of the wave energy with the speed of the particles being displaced. If the wave is a transverse wave, the particles of the medium are moving perpendicular to the direction of the wave energy motion. How fast the particles are moving at right angles determines the KE and the amplitude of the wave. How fast the energy moves along the axis of the wave is the frequency*wavelength (aka lambda). These are two different speeds (velocities) that are at right angles to each other.

hth
dsoz

 

[milski]

I'm still confused about this as well.

So one way to increase amplitude is to throw in more kinetic energy, correct? So increased kinetic energy means increased velocity.

If velocity = f*lambda, then doesn't increased velocity increase either (or both) lambda or frequency? And if increased velocity is necessary to increase KE, and KE is necessary to increase amplitude, then doesn't an increase in amplitude increase f and/or lambda?

There are two velocities here. One is the velocity of the particles moving perpendicular to the direction of the propagation of the wave. You throw more energy in, you increase the magnitude of this velocity which ends up manifesting as larger amplitude - it's the same thing as pushing a pendulum harder.

The other velocity is how fast the wave propagates, in other words how fast can you make the particles next to the ones that are already moving start to move. This one depends only on the properties of the media itself. If you particles move faster, they can be better at giving that energy to the 'neighbors' but now they have to give them more energy.

 

[silverice]

Don''t confuse the speed of the wave energy with the speed of the particles being displaced. If the wave is a transverse wave, the particles of the medium are moving perpendicular to the direction of the wave energy motion. How fast the particles are moving at right angles determines the KE and the amplitude of the wave. How fast the energy moves along the axis of the wave is the frequency*wavelength (aka lambda). These are two different speeds (velocities) that are at right angles to each other.

hth
dsoz

Ah! Thx!