3N3
is unpredictable

US.
1. Amirah ♥
2. Diana ♥
3. Grace ♥
4. Chriscilia ♥
5. Qianwei ♥
6. Hazhmirra ♥
7. Jermaine ♥
8. Norazlinda ♥
9. Adlin ♥
10. Diyanah ♥
11. Elisa ♥
12. Nurazreena ♥
13. Nursyahidah ♥
14. Atikah ♥
15. Pauline ♥
16. Pei lin ♥
17. Shafwani ♥
18. Shahirah ♥
19. Tabatha ♥
20. Salamah ♥
21. Vinis ♥
22. Sherlyn ♥
23. Daryl ♥
24. Dinie ♥
25. Iswandi ♥
26. Ivan ♥
27. Wende ♥
28. Jeremy ♥
29. Jingsheng ♥
30. Hairul ♥
31. Saiful ♥
32. Syafiq ♥
33. Keyang ♥
34. Taufiq ♥
35. Suthan ♥
36. Joel ♥
37. Zongxian ♥
38. Zulkifli ♥

TALK.

BYEBYE. Cheera Hazhmirra Jermaine Jingsheng

Physics.
Teacher-in-charge: Mr chio
Students: Adlin, Diyanah, Elisa, Grace, Jermaine, Jingsheng, Pauline, Qianwei, Saiful, Tabatha, Vinis, Wende, Zongxian,
Thursday, July 29, 2010 1:29 PM

Speed, distance and time
The following is a basic but important formula which applies when speed is constant (in other words the speed doesn't change):Speed = distance/time

Remember, when using any formula, the units must all be consistent. For example speed could be measured in m/s, distance in metres and time in seconds.If speed does change, the average (mean) speed can be calculated:Average speed = total distance travelled/total time taken

Example:If a car travels at a speed of 10m/s for 3 minutes, how far will it travel?Firstly, change the 3 minutes into 180 seconds, so that the units are consistent. Now rearrange the first equation to get distance = speed × time.Therefore distance travelled = 10 × 180 = 1800m = 1.8km

Units
In calculations, units must be consistent, so if the units in the question are not all the same (e.g. m/s, m and s or km/h, km and h), change the units before starting, as above.

In line (1), we divide by 60 because there are 60 minutes in an hour. Often people have problems working out whether they need to divide or multiply by a certain number to change the units. If you think about it, in 1 minute, the object is going to travel less distance than in an hour. So we divide by 60, not multiply to get a smaller number.

Velocity and acceleration
Velocity is the speed of a particle and its direction of motion (therefore velocity is a vector quantity, whereas speed is a scalar quantity).When the velocity (speed) of a moving object is increasing we say that the object is accelerating. If the velocity decreases it is said to be decelerating. Acceleration is therefore the rate of change of velocity (change in velocity / time) and is measured in m/s².

Distance-time graphs
These have the distance from a certain point on the vertical axis and the time on the horizontal axis. The velocity can be calculated by finding the gradient of the graph. If the graph is curved, this can be done by drawing a chord and finding its gradient (this will give average velocity) or by finding the gradient of a tangent to the graph (this will give the velocity at the instant where the tangent is drawn).

Velocity-time graphs/speed-time graphs
A velocity-time graph has the velocity or speed of an object on the vertical axis and time on the horizontal axis. The distance travelled can be calculated by finding the area under a velocity-time graph. If the graph is curved, there are a number of ways of estimating the area (see trapezium rule below). Acceleration is the gradient of a velocity-time graph and on curves can be calculated using chords or tangents, as above.

norazlinda
1:28 PM

Describing a journey made by an object is very boring if you just use words. As with much of science, graphs are more revealing.

Plotting distance against time can tell you a lot about a journey. Let's look at the axes:

Time always runs horizontally (the x-axis). The arrow shows the direction of time. The further to the right, the longer time from the start.

Distance runs vertically (the y-axis). The higher up the graph we go, the further we are from the start.

more info @ http://www.gcse.com/fm/dtg.htm


JERMAINE(:

1:27 PM

Like distance and time, speed and time can also be placed visually on a graph as well. A speed -time graph that has a slope greater than zero shows an object accelerating, graphs that shows a straight means a constant speed is being kept, and a negative slope means the car is decelerating. The steeper the slope, the faster it is either accelerating or decelerating.

This page will pose a new way of showing acceleration using a graph. Acceleration is the change in speed over time. Usually in a speed-time graph the speed is represented as the change in y (y) or the y-axis. The time is represented as the change in x (x) or the x-axis. The equation of the slope is still defined as the change in y divided by the change in x

Slope = (y/x)
WENDE
1:27 PM




Nurazreena(:
1:26 PM
[Video]E-Math: Speed-time Graph to Distance-time & Acceleration-time Graph

[Video]E-Math: Speed-time Graph to Distance-time & Acceleration-time Graph




JINGSHENG
1:25 PM

Labels:

1:24 PM
;D

Speed time Graph


Nursyahidah(:
1:24 PM

Labels:

1:23 PM

Distance - Time Graphs

Picture

Uniform Velocity means the object on the graph is moving equal distances in equal time.
This is why the sloped line (gradient) is a straight line.

The sloped line ( / ) on the graph is called the gradient, it represents the velocity.

To work out the gradient (velocity)
We take the vertical reading from the graph where the line finishes
and divide it by the horizontal reading where the line finishes.

gradient = vertical / horizontal = 50 / 5 = 10m/s

Diana
1:22 PM

Distance Time graphs are relatively simple. The next type of graph is Speed Time. These are more complicated, as they provide much more detail.

http://www.gcse.com/fm/dtg9.htm

Pauline.
1:20 PM

Distance-time graphs is a way to visually show a collection of data. It allows us to undertstand the relationships between the data.

Distance(m)
Time (s)

Distance (s) Time (s)
0 0
1 13
2 25
3 40
4 51
5 66
6 78


As you can see, the data from the table is shown in a visual format in the graph. The time(s) is shown as the x axis and the distance(m) is shown on the y axis on the graph. The points on the graph do not create a perfectly straight line so a line of best fit must be drawn in.


http://library.thinkquest.org/C0110840/dtgraph.htm

SHERLYN.
Thursday, July 22, 2010 1:19 PM

Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. Mirrors exhibit specular reflection.

In acoustics, reflection causes echoes and is used in sonar. In geology, it is important in the study of seismic waves. Reflection is observed with surface waves in bodies of water. Reflection is observed with many types of electromagnetic wave, besides visible light. Reflection of VHF and higher frequencies is important for radio transmission and for radar. Even hard X-rays and gamma rays can be reflected at shallow angles with special "grazing" mirrors.

BY SYAFIQ 3N3
1:11 PM

In fluid mechanics, displacement occurs when an object is immersed in a fluid, pushing it out of the way and taking its place. The volume of the fluid displaced can then be measured, as in the illustration, and from this the volume of the immersed object can be deduced (the volume of the immersed object will be exactly equal to the volume of the displaced fluid).

An object that sinks displaces an amount of fluid equal to the object's displaced volume. Thus buoyancy is expressed through Archimedes' Principle, which states that the weight of the object is reduced by its volume multiplied by the density of the fluid. If the weight of the object is less than this displaced quantity, the object floats; if more, it sinks. The amount of fluid displaced is directly related (via Archimedes' Principle) to its weight.

In the case of an object that sinks (is totally submerged), the volume of the object is displaced. In the case of an object that floats, the amount of fluid displaced will be equal in weight to the displacing object.

http://en.wikipedia.org/wiki/Displacement_(fluid)

Pauline.
1:11 PM

In physics, velocity is the rate of change of position. It is a vector physical quantity; both magnitude and direction are required to define it. The scalar absolute value (magnitude) of velocity is speed, a quantity that is measured in meters per second (m/s or ms−1) when using the SI (metric) system.

For example, "5 meters per second" is a scalar and not a vector, whereas "5 meters per second east" is a vector. The average velocity v of an object moving through a displacement during a time interval (Δt) is described by the formula:


The rate of change of velocity is acceleration – how an object's speed or direction changes over time, and how it is changing at a particular point in time.

http://en.wikipedia.org/wiki/Velocity

SHERLYN.
Thursday, July 15, 2010 1:34 PM

THIS IS ABT REFLECTION OF LIGHT
BY SYAFIQ
1:33 PM



NURAZREENA(:
1:29 PM
Refraction index

The refractive index (or index of refraction)
of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. For example, typical glass has a refractive index of 1.5, which means that light travels at math times the speed in air or vacuum. Two common properties of glass and other transparent materials are directly related to their refractive index. First, light rays change direction when they cross the interface from air to the material, an effect that is used in lenses and glasses. Second, light reflects partially from surfaces that have a different refractive index than their surroundings.



By ; nursyahidah.

Labels:

1:29 PM

The Critical Angle


In our introduction to TIR, we used the example of light traveling through water towards the boundary with a less dense material such as air. When the angle of incidence in water reaches a certain critical value, the refracted ray lies along the boundary, having an angle of refraction of 90-degrees. This angle of incidence is known as the critical angle; it is the largest angle of incidence for which refraction can still occur. For any angle of incidence greater than the critical angle, light will undergo total internal reflection.

So the critical angle is defined as the angle of incidence which provides an angle of refraction of 90-degrees. Make particular note that the critical angle is an angle of incidence value. For the water-air boundary, the critical angle is 48.6-degrees. For the crown glass-water boundary, the critical angle is 61.0-degrees. The actual value of the critical angle is dependent upon the combination of materials present on each side of the boundary.

adapted from http://www.physicsclassroom.com/class/refrn/u14l3c.cfm

JERMAINE,
1:27 PM
Critical angle


The total reflection of a beam of light at the interface of one medium and another medium of lower refractive index, when the angle of incidence to the second medium exceeds a specific critical angle.

If a beam of light passing through a medium A (say glass) strikes the boundary to a medium B of lower refractive index (say air) with a small angle of incidence i, part will be refracted, with an angle of refraction r, and part will be reflected (see illustration a). If i is increased it will reach a critical angle c, at which r = 90° (see illustration b). If i is now increased further, no refraction can occur and all the light energy is reflected by the interface (see illustration c). This total internal reflection occurs when c (given by nsinc = 1) is exceeded (n is the refractive index of A relative to B). The critical angle of optical glass is usually about 40° and total internal reflection is made use of by incorporating prisms in some optical instruments instead of mirrors.


Read more: total internal reflection - critical angle http://science.jrank.org/pages/20236/total-internal-reflection.html#ixzz0tj4EL2V0


Tabatha
1:26 PM

1:26 PM


When light strikes the interface between two materials, the light generally divides into two parts: reflected light (angle of incidence=angle of reflection) and refracted light. In order to find the angle of refraction we use Snell's Law.
There is another phenomenon called Total Internal Reflection. This is when the light ray enters the medium at its critical angle. This causes the light to bend such that it travels along the surface. Once the critical angle is exceeded, all the light gets reflected, thus no light gets refracted. This is TIR. Fiber-optic cables use this idea of TIR. The inside of the cable consists of glass while the outer layer is cladding. This is very practical in the field of medicine as we use it in such procedures as colonoscopy.
Total Internal Reflection
When light passes from a medium of longer refractive index into one of smaller refractive index (water to air), the refracted ray bends away from the normal.

Labels:

1:26 PM

Refractive Index

The refractive index is a constant for a given pair of materials. It can be defined as

speed of light in material 1

speed of light in material 2

This is usually written 1n2 and is the refractive index of material 2 relative to material 1. The incident light is in material 1 and the refracted light is in material 2.

If the incident light is in a vacuum this value is called the absolute refractive index of material 2. This is the value given in data books.

By definition the refractive index of a vacuum is 1. In practice, air makes little difference to the refraction of light with an absolute refractive index of 1.0008, so the value of the absolute refractive index can be used assuming the incident light is in air.

http://schools.matter.org.uk/SchoolsGlossary/refractive_index.html

Pauline.

1:25 PM

Refractive index

The refractive index or index of refraction is a ratio of the speed of light in a vacuum relative to that speed through a given medium (this quantity does not refer to an angle of refraction, which can be derived from the refractive index using Snell's Law). [note 1] In other words, as light passes from one medium to another as from air to water, the result is a bending of light rays at an angle. This physical property occurs because there is a change in the velocity of light going from one medium into another. Refractive index also describes the quantity that light is bent as it passes through a single substance. This involves calculating the angle at which light enters the medium and comparing that with the angle at which the light leaves the medium.[1][2][3]

Another view rates each substance with its own refractive index. This is because the velocity of light through the substance is compared as a ratio to the velocity of light in a vacuum. The velocity at which light travels in a vacuum is a physical constant, and the fastest speed at which energy or information can travel. However, light travels slower through any given material, or medium, that is not a vacuum. This is actually a delay from when light enters the material to when it leaves; i.e., when some is absorbed, and another part transmitted (See: light in a medium).[1][3][4][5]

A simplified, mathematical description of refractive index is as follows:

RI = velocity of light in a vacuum / velocity of light in medium

Hence, the RI of water is 1.33, meaning that light travels 1.33 times faster in a vacuum than it does in water.

Refractive index is also frequency dependent. In other words, the refractive index will vary according to the frequency of radiated light. This results in a slightly different refractive index for each color. Measurements are normally taken using the yellow light of a sodium source. Therefore, the cited values of refractive indexes such as 1.33 for water, are based on yellow light at a wavelength of 589.3 nanometers. One final note: temperature also affects refractive index, and cited values are based on a standard temperature.[1][2][3]

http://en.wikipedia.org/wiki/Refractive_index.

SHERLYN.
Wednesday, May 26, 2010 12:28 PM

At first we will look at a simpler reflection, one that happens on a flat surface. Below is a picture of such a situation. Here a single ray of light strikes a surface and is reflected from it.iswandi
12:27 PM

Diffuse Reflection:

When light is incident off of a rough or irregular surface, it can be defined as irregular of diffuse reflection. This occurs hen you look at the same lake on a windy day.

Diffuse reflection is reflection off of a rough or irregular opaque surface

Reflected rays are scattered

The formed image is not clearly defined

The Ð of incidence = Ð of reflection. The difference is that the surface is filled with different angles.

12:27 PM

When a ray of light hits a surface, it bounces off or reflects and then reaches our eyes. This phenomenon by which a ray of light changes the direction of propagation when it strikes a boundary between different media through which it cannot pass is described as the reflection of light.Or in simpler words reflection is the bouncing of light from a smooth surface.
There are two types of reflection of light:
Regular reflection or specular reflection
Irregular reflection or diffused reflection

Regular Reflection or Specular Reflection
Specular or regular reflection is the perfect, mirror-like reflection of light.
In this type of reflection the reflected rays are also parallel to each other.Reflection in a mirror, a water surface and highly polished floors, are examples of regular reflections .

norazlinda .
12:26 PM
Reflection of light.

REFLECTION OF LIGHT
Reflected waves are simply those waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter. When a wave approaches a reflecting surface, such as a mirror, the wave that strikes the surface is called the incident wave, and the one that bounces back is called the reflected wave (refer to figure 2-4). An imaginary line perpendicular to the point at which the incident wave strikes the reflecting surface is called the normal, or the perpendicular. The angle between the incident wave and the normal is called the angle of incidence.
The angle between the reflected wave and the normal is called the angle of reflection.








If the surface of the medium contacted by the incident wave is smooth and polished, each reflected wave will be reflected back at the same angle as the incident wave. The path of the wave reflected from the surface forms an angle equal to the one formed by its path in reaching the medium. This conforms to the law of reflection which states: The angle of incidence is equal to the angle of reflection.
Light waves obey the law of reflection. Light travels in a straight line through a substance of uniform density. For example, you can see the straight path of light rays admitted through a narrow slit into a darkened room. The straight path of the beam is made visible by illuminated dust particles suspended in the air. If the light is made to fall onto the surface of a mirror or other reflecting surface, however, the direction of the beam changes sharply.
The light can be reflected in almost any direction, depending on the angle with which the mirror is held.

Nursyahidah, 3N3(:

Labels:

12:26 PM



Source from: http://www.youtube.com/watch?v=hBQ8fh_Fp04

SHERLYN.
12:24 PM

Visit this link for the video.

http://www.youtube.com/watch?v=2P3nKJHO2j0&feature=related

DIANA.
12:23 PM

At first we will look at a simple refraction, one that happens at a flat boundary. Below is a picture of such a situation. Here a single ray of light strikes a boundary between two mediums and is refracted.

Here are descriptions for the terms in this diagram:

  • The ray of light which travels through the incident, or first, medium and strikes the boundary, or interface, is called the incident ray.
  • The ray of light which travels into the refracted, or second, medium and leaves the interface is called the reflected ray.
  • A line perpendicular to the surface is imagined at the point of refraction. This line is called a normal. In this context the word normal means perpendicular. In the above diagram the normal is colored blue.
  • The angle between the incident ray and the normal is called the angle of incidence, or the incident angle.
  • The angle between the refracted ray and the normal is called the angle of refraction, or the refracted angle.

The above picture demonstrates the general behavior of a light ray as it travels from air into some transparent medium such as water or glass.


http://id.mind.net/~zona/mstm/physics/light/rayOptics/refraction/refraction1.html

saiful ^^v

12:23 PM

The reflection of light is often discussed using phrases such as "a ray of light bounces off of a mirror." This is because when a light ray reflects at the surface of a mirror it follows a path similar in behavior to a pool ball bouncing off of a cushion on a pool table. However unusual it may sound at first, it is not really the best idea to describe the reflection of a light ray using words like bounce. It is better to describe light ray reflection as the turning back of the ray when it encounters the edge of a medium. Light rays, at least at first study, are best not quickly described in terms of particles, say, like pool balls.

At first we will look at a simpler reflection, one that happens on a flat surface. Below is a picture of such a situation. Here a single ray of light strikes a surface and is reflected from it.
Here are descriptions for the terms in this diagram:
The ray of light which strikes the surface is called the incident ray.
The ray of light which leaves the surface is called the reflected ray.
A line perpendicular to the surface is imagined at the point of reflection. This line is called a normal. In this context the word normal means perpendicular. In the above diagram the normal is colored blue.
The angle between the incident ray and the normal is called the angle of incidence, or the incident angle.
The angle between the reflected ray and the normal is called the angle of reflection, or the reflected angle.
Notice that the angle of incidence is equal to the angle of reflection.\
by syafiq
Friday, April 30, 2010 10:52 PM

What are the advantage and disadvantage of descending method of paper chromatography?

Advantage: The separation between the spots on the chromatogram will be greater.
Disadvantage: Separation may not be complete as the solvent will travel a longer distance due to gravitational pull.

Three forms of chromatography.
  • Paper chromatography.
  • Liquid chromatography.
  • Gas chromatography.
Basically, liquid chromatography involves the use of liquids that may incorporate hydrophilic, insoluble molecules, while gas chromatography involves the use of a gas to separate the substances being analysed.

★ SHERLYN.
10:14 PM
Chemistry e-learning

Question: What are the advantages and disadvantages of chromatography? and lastly,
look around the internet and see what are the different types of chromatography there are.

Answer: The advantages of chromatography is that it could separate very complex mixtures such as drugs, plastics, flavorings, tissue extracts, fuels, air samples, water samples and more. It requires a small amount of sample. It can be used to determine the number of components of a mixture clearly. The disadvantaged of chromatography is that paper chromatography has its limitations. Some mixtures are very difficult to separate by paper chromatography. It can't be used in quantitative analysis and doesn't allow the separation of complex mixtures.

The different types of chromatograhpy are,

Gas Chromatography
Liquid Chromatography
Ion Exchange Chromatography
Affinity Chromatography
Paper Chromatography
Thin paper Chromatography

All information is found on yahoo and google.com
Vinis
7:51 PM



From youtube.
http://www.youtube.com/watch?v=-fs5btFKdXA&feature=related
Pauline
7:34 PM

Chemistry e-learning.

What are the advantages and disadvantages of chromatography?

Advantages of Paper Chromatography: Why use paper chromatography? This method is quick to perform and easy to master. It can rapidly determine the number of constituents of a mixture sample. Paper chromatography even allows one to positively identify these constituents. Another advantage of this method is that it requires a relatively small sample and is very inexpensive.

Disadvantages of Paper Chromatography: Some mixtures are very difficult to separate by paper chromatography. Paper chromatography is solely an analytical method, not a preparative one. Because the sample size is so small, it is difficult to perform further analysis after the sample's contents have been chromatographically separated. This is in contrast to methods such as column chromatography, which are frequently use to preparatively separate larger amounts of mixtures. Lastly, paper chromatography can only be used in qualitative analysis. It is not possible to extract meaningful information about the quantitative content of a mixture from a paper chromatogram.

Different types of chromatography.
- Liquid chromatography.
- Gas chromatography.
- Thin-Layer Chromatography.
- Paper Chromatography.


Pauline.
Wednesday, April 21, 2010 8:40 PM
Longitudinal Waves & Transverse Waves .

Longitudinal Waves .







Longitudinal waves are waves which travels in a direction parallel to the direction of vibrations. It is demonstrated by rapidly pushing and pulling the end of a slinky coil.Between successive compressions is a stretched region , known as rarefaction . The coils themselves do not travel , they just vibrate forward and back . One examples of longitudinal waves is sound waves.Mechanical longitudinal waves have been also referred to as compressional waves or compression waves.


Transverse Waves .


Transverse waves are waves which travels in a direction perpendicular to the direction of the vibrations. It is demonstrated by moving the end of a slinky coil up and down or from side to side . Light and other electromagnetic waves are also transverse waves . Waves ropes and rope waves are examples of transverse waves.
Nursyahidah(:
12:29 PM

Longitudinal Waves

In a longitudinal wave the particle displacement is parallel to the direction of wave propagation. The animation below shows a one-dimensional longitudinal plane wave propagating down a tube. The particles do not move down the tube with the wave; they simply oscillate back and forth about their individual equilibrium positions. Pick a single particle and watch its motion. The wave is seen as the motion of the compressed region (ie, it is a pressure wave), which moves from left to right.

shahirah


12:26 PM

Transverse Waves

In a transverse wave the particle displacement is perpendicular to the direction of wave propagation. The animation below shows a one-dimensional transverse plane wave propagating from left to right. The particles do not move along with the wave; they simply oscillate up and down about their individual equilibrium positions as the wave passes by. Pick a single particle and watch its motion.

shahirah

12:21 PM

12:17 PM


In a longitudinal wave the particle displacement is parallel to the direction of wave propagation. The animation below shows a one-dimensional longitudinal plane wave propagating down a tube. The particles do not move down the tube with the wave; they simply oscillate back and forth about their individual equilibrium positions. Pick a single particle and watch its motion. The wave is seen as the motion of the compressed region (ie, it is a pressure wave), which moves from left to right.

In a transverse wave the particle displacement is perpendicular to the direction of wave propagation. The animation below shows a one-dimensional transverse plane wave propagating from left to right. The particles do not move along with the wave; they simply oscillate up and down about their individual equilibrium positions as the wave passes by. Pick a single particle and watch its motion.

for more info, go to http://paws.kettering.edu/~drussell/Demos/waves/wavemotion.html

Qianwei(:
12:17 PM

A transverse wave is a moving wave that consists of oscillations occurring perpendicular to the direction of energy transfer. If a transverse wave is moving in the positive x-direction, its oscillations are in up and down directions that lie in the y-z plane.

If you anchor one end of a ribbon or string and hold the other end in your hand, you can create transverse waves by moving your hand up-and-down. Notice though, that you can also launch waves by moving your hand side-to-side. This is an important point. There are two independent directions in which wave motion can occur. In this case, these are the y and z directions mentioned above. Further, if you carefully move your hand in a clockwise circle, you will launch waves that describe a left-handed helix as they propagate away. Similarly, if you move your hand in a counter-clockwise circle, a right-handed helix will form.


Saiful

12:15 PM

When energy moves from one place to another, it often travels in the form of a wave. This is in contrast with kinetic energy, which is energy an object has BECAUSE it is moving [also, not all moving energy is a wave: a battery can be thrown at someone, and it's stored energy does not suddenly become a wave]. A wave is an oscillation (or pulse) of energy travelling through some medium.

We generally describe two types of waves: transverse and longitudinal. A transverse wave is one in which the medium moves from side to side while the wave moves forward. An example of a transverse wave is an ocean swell: the energy may be moving towards shore, but in general the water molecules are moving up and down. For students who have studied trigonomentry, the sine and cosine waves are transverse.

[A transverse wave.]

In contrast, a longitudinal wave is one in which the pulse moves in the same direction as the medium. A good example of a longitudinal wave is a sound wave. Some source of vibration compresses and rarifies molecules of air, and the pulse moves outward to be heard. The molecules wobble back and forth but do not move overall (to prove this to yourself, remember that even though the speed of sound is about 700 miles per hour, you hardly ever cause a hurricane just by speaking!


[A longitudinal, or compression wave.]

All waves can be described with the same mathematical tools. The part of a wave have specific names. The high point is called the crest, and the low point is called the trough. The distance between two consecutive crests (or troughs) is called the wavelength. The difference between the highest and lowest points of a wave are called it's amplitude (and can be increased with an amplifier), and a point in space through which a wave passes without causing action is called a node. Finally, an observer watching waves pass by will be able to count the frequency, how many waves pass in a given length of time.


[A labeled transverse wave]

It is relatively easy to picture the descriptions above with with relation to a tranverse wave, but many students have trouble seeing how they can apply to a longitudinal wave like a sound wave. The key is to remember that all our descriptions of waves will be mathematical. In this case, you could graph the density of a longitudinal wave, and the result is a longitudinal wave.


[A transverse and longitudinal wave. Notice that the transverse wave is a graph of ink used in the longitudinal wave.]





Hazhmirra :D

12:15 PM



1-5 TRANSVERSE WAVES To explain transverse waves, we will again use our example of water waves. Figure 1-3 is a cross section diagram of waves viewed from the side. Notice that the waves are a succession of crests and troughs. The wavelength (one 360 degree cycle) is the distance from the crest of one wave to the crest of the next, or between any two similar points on adjacent waves. The amplitude of a transverse wave is half the distance measured vertically from the crest to the trough. Water waves are known as transverse waves because the motion of the water is up and down, or at right angles to the direction in which the waves are traveling. You can see this by observing a cork bobbing up and down on water as the waves pass by; the cork moves very little in a sideways direction. In figure 1-4, the small arrows show the up-and-down direction the cork moves as the transverse wave is set in motion. The direction the wave travels is shown by the large arrow. Radio waves, light waves, and heat waves are examples of transverse waves.

NURAZREENA
12:15 PM

12:12 PM

Another example of waves with both longitudinal and transverse motion may be found in solids as Rayleigh surface waves. The particles in a solid, through which a Rayleigh surface wave passes, move in elliptical paths, with the major axis of the ellipse perpendicular to the surface of the solid. As the depth into the solid increases the "width" of the elliptical path decreases. Rayleigh waves are different from water waves in one important way. In a water wave all particles travel in clockwise circles. However, in a Rayleigh surface wave, particles at the surface trace out a counter-clockwise ellipse, while particles at a depth of more than 1/5th of a wavelength trace out clockwise ellispes. The movie below shows a Rayleigh wave travelling from left to right along the surface of a solid. I have identified two particles in blue to illustrate the counterclockwise-clockwise motion as a function of depth.

Syafiq 3n3
12:07 PM



In physics, oscillation that is propagated from a source. Mechanical waves require a medium through which to travel. Electromagnetic waves do not; they can travel through a vacuum. Waves carry energy but they do not transfer matter. The medium (for example the Earth, for seismic waves) is not permanently displaced by the passage of a wave. The model of waves as a pattern is used to help understand the properties of light and sound. Experiments conducted in a ripple tank with water waves can explain how waves slow down as water becomes shallower, how waves change direction when travelling through another medium, and how waves are reflected from different surfaces. See also standing wave.


Types of wave
There are various ways of classifying wave types. One of these is based on the way the wave travels. In a transverse wave, the displacement of the medium is perpendicular to the direction in which the wave travels. An example of this type of wave is a mechanical wave projected along a tight string. The string moves at right angles to the wave motion. Electromagnetic waves are another example of transverse waves. The directions of the electric and magnetic fields are perpendicular to the wave motion. In a longitudinal wave the disturbance takes place parallel to the wave motion. A longitudinal wave consists of a series of compressions and rarefactions (states of maximum and minimum density and pressure, respectively). Such waves are always mechanical in nature and thus require a medium through which to travel. Sound waves are an example of longitudinal waves. Waves that result from a stone being dropped into water appear as a series of circles. These are called circular waves and can be generated in a ripple tank for study. Waves on water that appear as a series of parallel lines are called plane waves.
12:07 PM
Properties of Waves


Waves have properties that can be measured. All waves are made by adding sine waves. Here is a picture of a sine wave: Wave.png
Sine waves can be measured too. The shape of a sine wave is given by its amplitude, phase, wavelength and frequency. The speed that the sine wave moves can be measured. The amplitude and wavelength of the sine wave is shown in the picture.

The highest point on a wave is called the peak. The lowest point is called the trough. The peak of a wave and the trough of a wave are always twice the wave's amplitude apart from each other. The part of the wave half way in between the peak and the trough is called the baseline.

All waves are made by adding up sine waves. Waves also have amplitudes, phases, wavelengths, frequencies and speeds that can be measured.
-NurAdlin
12:05 PM
Transverse and Longitudinal Waves



Transverse Waves

For the displacement of the medium is perpendicular to the direction of propagation of the wave.


Transverse waves cannot propagate in a gas or a liquid because there is no mechanism for driving motion perpendicular to the propagation of the wave.

Longitudinal Waves
In longitudinal waves the displacement of the medium is parallel to the propagation of the wave. A wave in a "slinky" is a good visualization. Sound waves in air are longitudinal waves.

Shafwani Natasyah
12:05 PM
Longitudinal wave



Source from youtube (:

NURAZREENA
12:03 PM


A transverse wave is a moving wave that consists of oscillations occurring perpendicular to the direction of energy transfer.Longitudinal waves are waves that have the same direction of oscillation or vibration along their direction of travel, which means that the oscillation of the medium (particle) is in the same direction or opposite direction as the motion of the wave.Examples of longitudinal waves include sound waves. An example of a transverse wave is water waves.


Keyang
12:03 PM



In a longitudinal wave the particle displacement is parallel to the direction of wave propagation. The animation below shows a one-dimensional longitudinal plane wave propagating down a tube. The particles do not move down the tube with the wave; they simply oscillate back and forth about their individual equilibrium positions. Pick a single particle and watch its motion. The wave is seen as the motion of the compressed region (ie, it is a pressure wave), which moves from left to right.



In a transverse wave the particle displacement is perpendicular to the direction of wave propagation. The animation below shows a one-dimensional transverse plane wave propagating from left to right. The particles do not move along with the wave; they simply oscillate up and down about their individual equilibrium positions as the wave passes by. Pick a single particle and watch its motion.

Iswandi cute:D
12:02 PM

A transverse wave is a moving wave that consists of oscillations occurring perpendicular to the direction of energy transfer. If a transverse wave is moving in the positive x-direction, its oscillations are in up and down directions that lie in the y-z plane.

If you anchor one end of a ribbon or string and hold the other end in your hand, you can create transverse waves by moving your hand up-and-down. Notice though, that you can also launch waves by moving your hand side-to-side. This is an important point. There are two independent directions in which wave motion can occur. In this case, these are the y and z directions mentioned above. Further, if you carefully move your hand in a clockwise circle, you will launch waves that describe a left-handed helix as they propagate away. Similarly, if you move your hand in a counter-clockwise circle, a right-handed helix will form. These phenomena of simultaneous motion in two directions go beyond the kinds of waves you can create on the surface of water; in general a wave on a string can be two-dimensional. Two-dimensional transverse waves exhibit a phenomenon called polarization. A wave produced by moving your hand in a line, up and down for instance, is a linearly polarized wave, a special case. A wave produced by moving your hand in a circle is a circularly polarized wave, another special case. If your motion is not strictly in a line or a circle your hand will describe an ellipse and the wave will be elliptically polarized.

Electromagnetic waves behave in this same way, although it is harder to see. Electromagnetic waves are also two-dimensional transverse waves.

Ray theory does not describe phenomena such as interference and diffraction, which require wave theory (involving the phase of the wave). You can think of a ray of light, in optics,as an idealized narrow beam of electromagnetic radiation. Rays are used to model the propagation of light through an optical system, by dividing the real light field up into discrete rays that can be computationally propagated through the system by the techniques of ray tracing. [1] A light ray is a line or curve that is perpendicular to the light's wavefronts (and is therefore collinear with the wave vector). Light rays bend at the interface between two dissimilar media and may be curved in a medium in which the refractive index changes. Geometric optics describes how rays propagate through an optical system.[1]

This two-dimensional nature should not be confused with the two components of an electromagnetic wave, the electric and magnetic field components, which are shown in the electromagnetic wave diagram here. The light wave diagram shows linear polarization. Each of these fields, the electric and the magnetic, exhibits two-dimensional transverse wave behavior, just like the waves on a string.

The transverse plane wave animation shown is also an example of linear polarization. The wave shown could occur on a water surface.



Muhd Syafiq Bin Fadzil 3n3
12:01 PM

Characteristics of Waves:

Wave speed (v) is the velocity of the wave as it moves through a medium. Wave speed is also known as the propagation speed of the wave. The speed of a wave is expressed in m/s.

Speed on a string (transverse): where F is the tension (N), m/L is the mass per unit length (Kg/m)

Speed through a metal rod (longitudinal): where Y is young’s modulus (N/m2) and ρ is the density (usually in units of Kg/m3).

Speed through a gas or liquid: Where β is the bulk modulus and ρ is the density.

Wavelength (λ) is the distance between corresponding points on adjacent wave pulses. The wavelength of a wave is expressed in linear units, usually meters.

Frequency (ƒ) is the number of complete waves, which pass through a point in space per unit time. The frequency of waves is measured in Hertz (Hz). An older but more descriptive unit is cycles per second (cps).

The period (T) of a wave is the time required for a complete wave to pass through a point in space. The period is the inverse of the frequency ( T = 1 / ƒ ). The period of a wave is measured in seconds.

Amplitude (a) is the maximum displacement experienced by a particle as the result of a wave. The amplitude is a measure of the energy carried by a wave. The units for amplitude are specialized for the type of wave. The amplitude of waves at the beach can be measured in meters. The amplitude of sound waves is measured in a unit of pressure such as Pascals. Amplitude is independent of the other wave characteristics.

The wave equation ( v = ƒ x λ ) expresses the relationship between wave speed (v), frequency ( ƒ ), and wavelength (λ). The wave equation shows that frequency and wavelength are inversely proportional. The wave equation is useful in many different applications and may be utilized in the analysis of matter waves as well as electromagnetic waves. http://web.me.com/dtrapp/ePhysics.f/WDwaves.html shahirah
12:00 PM




<=Plane pressure wave

Longitudinal waves are waves that have the same direction of oscillation or vibration along their direction of travel, which means that the oscillation of the medium (particle) is in the same direction or opposite direction as the motion of the wave. Mechanical longitudinal waves have been also referred to as compressional waves or compression waves.




Saiful












12:00 PM
Transverse and Longitudinal Waves



Found on www.youtube.com

Labels:

11:59 AM
Longitudinal waves





VIDEO FROM YOUTUBE.

Tabatha
Thursday, April 15, 2010 3:50 PM

By extension, the term is also used to describe waves that are approximately plane waves in a localized region of space. For example, a localized source such as an antenna produces a field that is approximately a plane wave in its far-field region. Equivalently, for propagation in a homogeneous medium over lengthscales much longer than the wavelength, the "rays" in the limit where ray optics is valid correspond locally to approximate plane waves.

Mathematically, a plane wave is a wave of the following form:


where i is the imaginary unit, k is the wave vector, ω is the angular frequency, and A is the (complex) amplitude. This form of the plane wave uses the physics time convention; in the engineering time convention, –j is used instead of +i in the exponent. The physical solution is found by taking the real part of this expression:


This is the solution for a scalar wave equation in a homogeneous medium. For vector wave equations, such as the ones describing electromagnetic radiation or waves in an elastic solid, the solution for a homogeneous medium is similar: the scalar amplitude A is replaced by a constant vector A. For example, in electromagnetism A is typically the vector for the electric field, magnetic field, or vector potential. A transverse wave is one in which the amplitude vector is orthogonal to k, which is the case for electromagnetic waves in an isotropic medium. By contrast, a longitudinal wave is one in which the amplitude vector is parallel to k, such as for acoustic waves in a gas or fluid.

In this equation, the function ω(k) is the dispersion relation of the medium, with the ratio ω/|k| giving the magnitude of the phase velocity and dω/dk giving the group velocity. For electromagnetism in an isotropic medium with index of refraction n, the phase velocity is c/n, which equals the group velocity only if the index is not frequency-dependent.

Generally, a wave solution can be expressed as a superposition of plane waves. This approach is known as the Angular spectrum method. The form of the planewave solution is actually a general consequence of translational symmetry. More generally, for periodic structures having discrete translational symmetry, the solutions take the form of Bloch waves, most famously in crystalline atomic materials but also in photonic crystals and other periodic wave equations. As another generalization, for structures that are only uniform along one direction x (such as a waveguide along the x direction), the solutions (waveguide modes) are of the form exp[i(kx-ωt)] multiplied by some amplitude function a(y,z)

Nurazreena(:

Labels:

2:27 PM
Wave power

Wave power is a form of alternative energy which harnesses the natural movements of the world's oceans. In the late 1990s, a number of firms began to explore the possibility of wave power, and in the early 2000s, a number of experimental installations were made around the world to see how feasible wave power could be. It is believed that if harnessed correctly, wave power could generate massive amounts of electricity which could be used to do things like run desalination plants, power water treatment facilities, and power homes and businesses for consumers. As a result of early success, several nations became more invested in the idea.

The concept takes advantage of the already abundant energy in the ocean, which manifests in the rise and fall of water in the form of waves. One of the easiest ways to capture this energy is through a simple air chamber. As the waves rise and fall in the chamber, they force air through the top, spinning aturbine which can be used in electricity generation. These chambers can be mounted on the shoreline, or they can be located out at sea in the form of large floating buoys.

There are a number of significant advantages to wave power which make it quite appealing to fans of alternative energy. The first is that wave power is a truly renewable energy source, since it takes advantage of already occurring natural processes. In addition, wave power is relatively low cost once facilities are installed, and especially if it is used locally, the cost of moving the power around are fairly minimal as well. Wave power facilities also would not take up valuable land, as is the case with solar arrays and wind farms.

There are also some concerns about wave power, although most of these concerns are aesthetic. Critics claim that people will find the appearance of wave power facilities unpleasant, and that this form of power generation could ruin many excellent views. Wave power will only succeed in certain high energy areas of the ocean, and many of these areas are also beautiful and popular vacation spots. Critics are also concerned about the noise, which could be significant. In addition to disrupting human life, the noise might also be distracting for animals which call the ocean home.

Many of the concerns about wave energy are valid, but proponents of the technology hope that the benefits will ultimately outweigh these concerns. Many major energy companies seem to agree, since a number of companies have invested in significant research on wave energy. Governments have also promoted the technology as a green alternative to other methods of electricity generation.

Credits : http://www.wisegeek.com/what-is-wave-power.htm

Joel

1:44 PM

wave

A wave is a phenomenon in which energy is transferred through vibrations.
A wave carries energy away from the wave source


The effect of a rope waves can be seen by fixing one end of a rope by tying it around a rod and moving the other end up and down.
12:50 PM

Longitudinal Waves : Sound
While waves on a string or in water are transverse, sound waves are longitudinal. The term longitudinal means that the medium transmitting the waves—air, in the case of sound waves—oscillates back and forth, parallel to the direction in which the wave is moving. This back-and-forth motion stands in contrast to the behavior of transverse waves, which oscillate up and down, perpendicular to the direction in which the wave is moving.
Imagine a slinky. If you hold one end of the slinky in each of your outstretched arms and then jerk one arm slightly toward the other, you will send a pulse across the slinky toward the other arm. This pulse is transmitted by each coil of the slinky oscillating back and forth parallel to the direction of the pulse.
When the string on a violin, the surface of a bell, or the paper cone in a stereo speaker oscillates rapidly, it creates pulses of high air pressure, or compressions, with low pressure spaces in between, called rarefactions. These compressions and rarefactions are the equivalent of crests and troughs in transverse waves: the distance between two compressions or two rarefactions is a wavelength.
Pulses of high pressure propagate through the air much like the pulses of the slinky illustrated above, and when they reach our ears we perceive them as sound. Air acts as the medium for sound waves, just as string is the medium for waves of displacement on a string. The figure below is an approximation of sound waves in a flute—each dark area below indicates compression and represents something in the order of 1024 air molecules.

WEN DE
12:34 PM
Longitudinal waves



Google.com

Tabatha.
10:09 AM

Longitudinal wave.



Animation courtesy of Dr. Dan Russell, Kettering University


Pauline.
10:05 AM



Pauline.

9:36 AM

Longitudinal Waves.

In a longitudinal wave the particle displacement is parallel to the direction of wave propagation. The animation below shows a one-dimensional longitudinal plane wave propagating down a tube. The particles do not move down the tube with the wave; they simply oscillate back and forth about their individual equilibrium positions. Pick a single particle and watch its motion. The wave is seen as the motion of the compressed region (ie, it is a pressure wave), which moves from left to right.


Transverse Waves.

In a transverse wave the particle displacement is perpendicular to the direction of wave propagation. The animation below shows a one-dimensional transverse plane wave propagating from left to right. The particles do not move along with the wave; they simply oscillate up and down about their individual equilibrium positions as the wave passes by. Pick a single particle and watch its motion.


http://paws.kettering.edu/~drussell/Demos/waves/wavemotion.html

Pauline.
9:24 AM

Transverse wave.



Video error occured? Visit this link http://www.youtube.com/watch?v=Kbd8QUkRbjw

★SHERLYN.
9:11 AM

if you cant play the video, here is the link

Diana