Why waters wave become round when we throw anything in the water?

[whyonlyme]

For example I throw stone in the pool or river. From where stone touched the water there

becomes waves in the water. My question is Why it become like a circle not like square or any

other shape? Can anyone give the reason??

 

[RandomGuy88]

I would think it is because the energy has to go somewhere and there is no preferred direction of travel for that energy, it travels uniformly through the water. If it were to form a square that means that the energy near the corners of the square traveled faster than the energy on the sides.

 

[JesseC]

Is it not because a stone is to first approximation a small sphere?

So if you threw the stone into a pond, relatively far away from yourself, it looks like a point source. Thus even if the stone is quite irregularly shaped, its small enough produce approximately circular wave fronts.

If you dropped a big square box into a pond, the waves produced would be square with rounded corners. I can't imagine spherical waves being produced in that case.

 

[Steger]

Is it not because a stone is to first approximation a small sphere?

So if you threw the stone into a pond, relatively far away from yourself, it looks like a point source. Thus even if the stone is quite irregularly shaped, its small enough produce approximately circular wave fronts.

If you dropped a big square box into a pond, the waves produced would be square with rounded corners. I can't imagine spherical waves being produced in that case.

Not quite I'd say, but an interesting take.

If you like, it's because of Huygens' Principle http://en.wikipedia.org/wiki/Huygens_principle or alternately because, as was stated, water is isotropic (it's the same in every direction, no preferred direction). Here's a random picture I found on the web:

http://gilmore2.chem.northwestern.edu/images2/e_huygen.gif

 

[janger]

If you like, it's because of Huygens' Principle

But say if you drop a square object in the pond. The wave would still emanate outwards at the corner points with the same speed as every other point, thus keeping the square-shaped ripple?

I think it has to do with how ripples are formed in the first place. They are caused by oscillations in the water. An object dropped into water first displaces some of the water. Some is pushed outward, upward and downward. As the object sinks it leaves a depression or void which is lower than the surrounding water's surface. The surrounding water moves inward and upward to quickly fill the void. Due to it's kinetic energy, some is pushed upwards into the air, higher than the surrounding water level. As this water column falls back down the kinetic energy makes it "overshoot" and it creates another depression, though smaller than the first. The cycle repeats until all the energy has dissipated. That's why you get several ripples instead of one.

So I think what happens is the column of water, even though it may begin forming as a square shape, becomes rounded due to the isotropic nature, cohesive forces and maybe even surface tension.

Watch this vid for a water drop example:

 

[Steger]

Is it not because a stone is to first approximation a small sphere?

So if you threw the stone into a pond, relatively far away from yourself, it looks like a point source. Thus even if the stone is quite irregularly shaped, its small enough produce approximately circular wave fronts.

If you dropped a big square box into a pond, the waves produced would be square with rounded corners. I can't imagine spherical waves being produced in that case.

Actually, after thinking about it, I believe this is correct. Essentially we're taking Huygens' Principle and only looking at terms in its expansion which survive in the far field limit r \rightarrow \infty

 

[whyonlyme]

I've posted this question on yahoo answers. I've received this answer.

Only the water is drawn to Earth spherically, which means that any noise or other weaker waves are soon absorbed by the forces immediately around the object. One should not forget, that these ripples, or waves are in 3 dimensions, and are as such traveling in all directions spherically from the source object hitting the water. The object emits sound energy to the upper half of the sphere into the air, whilst emitting the other physical energy towards the lowers potion of the sphere, into the surrounding water. The waves on the surface are exposed to less pressure and will thus travel further than the waves beneath the object. These waves of energy attempt to equalise almost instantaneously due to the forces of gravity and motion. However, in less dense situations, like for example a gaseous chemical, the effect is not so abrupt, and one can have time to physically see the square or odd shaped initial radiated waves, though still, these waves will, in time, equalise them self out by Cancelling out the weaker forces leaving just the renowned circle.

One other aspect is also the many other wave forms emitted from the object hitting the surface, that of course is sound, and as can once again be identified by sound sampling, are the inconsistencies in the emitted wave.

Your absolutely right, it does happen as you would expect, only its all happening so fast, and all energies seek to become equal or in equilibrium x

But I didn't understand that.. :P

 

[whyonlyme]

I've posted this question on yahoo answers. I've received this answer.

Only the water is drawn to Earth spherically, which means that any noise or other weaker waves are soon absorbed by the forces immediately around the object. One should not forget, that these ripples, or waves are in 3 dimensions, and are as such traveling in all directions spherically from the source object hitting the water. The object emits sound energy to the upper half of the sphere into the air, whilst emitting the other physical energy towards the lowers potion of the sphere, into the surrounding water. The waves on the surface are exposed to less pressure and will thus travel further than the waves beneath the object. These waves of energy attempt to equalise almost instantaneously due to the forces of gravity and motion. However, in less dense situations, like for example a gaseous chemical, the effect is not so abrupt, and one can have time to physically see the square or odd shaped initial radiated waves, though still, these waves will, in time, equalise them self out by Cancelling out the weaker forces leaving just the renowned circle.

One other aspect is also the many other wave forms emitted from the object hitting the surface, that of course is sound, and as can once again be identified by sound sampling, are the inconsistencies in the emitted wave.

Your absolutely right, it does happen as you would expect, only its all happening so fast, and all energies seek to become equal or in equilibrium x

But I didn't understand that.. :P

 

[Containment]

Do a science experiment to find the answer out this is one you can do with a bucket of water a pan filled with water and some different shaped objects.

 

[FizixFreak]

I've posted this question on yahoo answers. I've received this answer.

Only the water is drawn to Earth spherically, which means that any noise or other weaker waves are soon absorbed by the forces immediately around the object. One should not forget, that these ripples, or waves are in 3 dimensions, and are as such traveling in all directions spherically from the source object hitting the water. The object emits sound energy to the upper half of the sphere into the air, whilst emitting the other physical energy towards the lowers potion of the sphere, into the surrounding water. The waves on the surface are exposed to less pressure and will thus travel further than the waves beneath the object. These waves of energy attempt to equalise almost instantaneously due to the forces of gravity and motion. However, in less dense situations, like for example a gaseous chemical, the effect is not so abrupt, and one can have time to physically see the square or odd shaped initial radiated waves, though still, these waves will, in time, equalise them self out by Cancelling out the weaker forces leaving just the renowned circle.

One other aspect is also the many other wave forms emitted from the object hitting the surface, that of course is sound, and as can once again be identified by sound sampling, are the inconsistencies in the emitted wave.

Your absolutely right, it does happen as you would expect, only its all happening so fast, and all energies seek to become equal or in equilibrium x

But I didn't understand that.. :P

Well what part you don't understand?
any way coming back to your question you must be completely familiar with the law of conservation of energy to understand this scenario see when the energy of the pebble or any object is targeted towards the surface of the water(i.e when the object hits the surface of the water) the K.E of the object is absorbed by the surface and seen in two forms
(1)the sound energy that is above the surface
(2)the waves that form on the surface and below the surface
the waves below the surface are not very prominent because below the surface the pressure is higher compares the surface it self so waves below the surface diminish so you see the the energy of the object is scattered in the environment in a spherical path one part of the sphere is above surface and other on the surface and below it the reason why the waves are formed in a circul is because of the fact that the water itself acts as a medium for channeling the energy the rate at which the energy travels through the medium depends on the density and composition of the medium and since the surface of the water has same composition and density the energy travels through every point at the same rate if you take a liquid which has different density at different points and repeat the experiment the waves will not be formed in a circular pattern now the waves are formed not only on the surface but above it as well(sound waves) can you guess both these types of waves travel at the same rate or not? and if they don't then why?
let me know if this helped you there are also different ways to answer your question.

 

[Ranger Mike]

is become round for same reason rain drop hits floor then becomes round - a Circle is the one geometric form that has equal force in all directions..in the case of water drop, it handles atmospheric pressure of 14.7 PSI equally in 360 degrees as well as surface tension, regarding wave...it handle surface tension equally in all directions AFTER interaction with waves...

 

[Dadface]

Is it not because a stone is to first approximation a small sphere?

So if you threw the stone into a pond, relatively far away from yourself, it looks like a point source. Thus even if the stone is quite irregularly shaped, its small enough produce approximately circular wave fronts.

If you dropped a big square box into a pond, the waves produced would be square with rounded corners. I can't imagine spherical waves being produced in that case.

Correct.The shape of the wavefronts depend on two main factors one being the shape of the object used.In ripple tanks,which are used to demonstrate wave properties,circular wavefronts are generated by using spherical or point dippers and plane wavefronts are generated by using straight edged dippers.As described by Jesse the edges are rounded.
The second factor is the the speed of the waves.A point dipper will produce circular wavefronts only if the waves travel with equal speeds in all directions.The speed is dependent on other factors such as the depth of the water.In ripple tanks refraction is demonstrated by arranging for the waves to travel from one depth of water to another eg into shallower water where they slow down.For the small depths used in ripple tanks the changes of speed can be appreciable.

 

[sophiecentaur]

That yahoo answers paragraph reads like something written in the eighteenth century. Any serious explanation that talks about thing "attempting" to do anything and which confuses force with energy must be seriously suspect and should be read with care. The passage looks as if it could be a dodgy translation. (What's a "renowned circle"?)
If you drop a square box in the water, the initial wave will look square. The Huygens idea is just what you want for explaining what happens next. Each, elemental, part along the whole of the (initially square) wavefront will spread out into a circle (travelling at wave speed) and mix with the waves from every other elemental part. These expanding circular waves will add constructively and destructively in such a way as to produce an expanding wave with increasingly rounder and rounder corners and it tends a circle as it gets further and further away.
There is another mechanism at work - dispersion, because the different wavelengths, which go together to make the original 'peaky' shape, travel at different speeds. This will alter the shape of the wave (height) as it progresses, from a sharp peak (where the box hits the water) to a flatter and more rounded / extended shape. This will also tend to blurr out the flat sides of this expanding square shape.

 

[Dadface]

If a square dipper is used the wave does look square but with rounded edges at each corner.As the wave progresses the lengths of the rounded sections increase compared to the lengths of the linear sections.

 

[sophiecentaur]

With a big enough tank and with sensitive enough measuring equipment, it would go circular eventually.