Waves And Types Of Waves 6u4n22

Waves and Types of Waves

Submitted to: Sir Usman Submitted by: Muhammad Usman (08-chem-02-B)

Date: 11may, 2009

Department of Chemical Engineering University of Engineering and Technology Lahore

“(Or

[the state of a disbeliever] is like the darkness in a vast deep sea, overwhelmed with waves topped by waves, topped by dark clouds, (layers of) darkness upon darkness: if a man stretches out his hand, he can hardly see it! And he for whom Allah has not appointed light for him there is no light.) ” Quran, 24:40)

(Al-

Contents Water waves:................................................................................... ..........................7 Propagation of waves:............................................................................................ .7 1.

Mechanical waves:...........................................................................................8 Examples:............................................................................................. ...............8

2.

Electromagnetic waves:...................................................................................9 Examples:............................................................................................. ...............9

1.

Transverse waves:...............................................................................................9 Explanation:................................................................................................... .........9

Examples:............................................................................................. ...............9 2.

Longitudinal waves:............................................................................. ..............10 Explanation:................................................................................................. .........10 Example:.......................................................................................................... ..10

3.

Surface waves:..................................................................................................10

Note:..................................................................................................... ...................13 1.

One dimensional waves:....................................................................................11 Example:........................................................................................................ .......11

2.

Two dimensional waves:....................................................................................11 Example:........................................................................................................ .......11 Explanation:................................................................................................... ....11

3.

Three dimensional waves:.................................................................................11 Example:........................................................................................................ .......11 Wavefronts:.......................................................................................................12 Ray:................................................................................................................... .12 1.

Plane waves:..................................................................................................12

2.

Spherical waves:............................................................................................. 12

1.

Travelling waves/progressive waves:..............................................................13

2.

Standing waves/stationary waves:.................................................................13 Explanation:................................................................................................... ....13

Summary: A Wave is a disturbance that travels through a medium from one location to another location. There lies a close relationship between a wave and a pulse. A pulse is a single wave travelling through a medium while if this disturbance continues to travel periodically and over a prolonged period of time from one location of medium to the other part of medium then it is referred as wave. A medium is a substance or material which carries the waves. Waves are transmitted through the medium by the interaction of some particles present in the medium which move and interact with their next particle and thus waves are transmitted. Some interacting particles in case of different media are e.g.

Sound waves………….. Air molecules Slinky waves……………individual coils of slinky spring Waves are the disturbances that transport energy from one place to another place without transport of matter. Hence waves are said to be an energy transport phenomena and this property of waves differentiates them from other types of phenomena’s in which energy transfer is taking place but in somewhat different way. There are different types of waves present. Waves can be classified regarding to some of their properties e.g. ➢ Regarding their ability to transmit energy through vacuum 1. Mechanical waves (which needs medium to and cannot

transmit energy through vacuum) • Examples are sound waves 2. Electromagnetic waves (no need of medium to and can transmit energy through vacuum) • Examples are light waves ➢ Regarding the motion of particles of medium during the disturbance 1. Transverse waves (motion of particles perpendicular to propagation of waves) • Examples are waves introduced in a string piece 2. Longitudinal waves (motion of particles parallel to propagation of waves) • Examples are sound waves 3. Surface waves (motion of particles is circular as the waves es through)

Waves: “A wave is a disturbance that propagates through space and time, usually with the transference of energy.” Explanation: To define what is a wave is somewhat a difficult thing. Usually we say that a wave is a disturbance in which energy of vibration is transferred from source point to another point (but a vibration is not necessarily a wave) within a medium but there is some problem when we handle with stationary waves because in that case energy is moving in both directions equally.

Also in case of electromagnetic waves there is no concept of medium. So it is somewhat confusing. All the waves have some special features and they fulfill these criteria… Reflection……wave’s direction changes after hitting a reflective surface Refraction……wave direction changes due to change in speed while entering in a new medium Diffraction……wave’s when interact with obstacles in their path they are bend Dispersion…….they can split up by their frequency Rectilinear motion…..they always follow the straight path

Examples: Examples of waves are 1. 2. 3. 4.

Sound waves Water surface waves Gravitational waves Electromagnetic waves etc.

Production of waves: Waves are the disturbances that are propagated by medium. Since waves are disturbances, waves can be generated. Some cases how waves can be produced are as follows…

Water waves: In water waves are generated by some sort of disturbance in water medium. If we throw a rock, stone or a pebble in static water we see that disturbance is created over its surface and effects of which are transferred from the source point of disturbance towards outwards radially. Similar types of waves are generated when a duck floats over water surface shaking its tail. Also when we put a nib of pencil in a tub of water and move it up and down waves is generated and these generated waves are propagated. There may be two different types of waves generated in water surface

1. Plane waves: Waves that travel together as a front in a straight line direction Example:

In case of a sea the waves that comes out towards sandy shore perhaps, are called plane waves

2. Circular waves: The waves which originate from the point where disturbance occurs and move radially outwards over water surface Example: Waves that are generated over water surface by throwing a pebble into water.

Propagation of waves: Waves travel in the form of crest and troughs. Every crest is often followed by a next crest. Two crests are separated by a trough and in this way an alternating pattern is formed. Crest: A crest is a point on a wave where particles of medium have maximum phase of vibration. Trough: A trough is a point on a wave where particles of medium have minimum phase of vibration.

C fica of waves:

lassi tion

Waves are of many kinds. All possess some common properties but they are somewhat different from each other so that we can classify them regarding some of their properties. Some common types of classification are as follows…

Ability/inability to be transmitted through vacuum 1. Mechanical waves: These are the waves which cannot transmit energy through vacuum and so they cannot through it. Commonly these are the waves which need any material medium to and transmit any kind of energy or disturbance from one place (source point) to another place. Examples: a. A common example of mechanical waves is the sound waves which needs the material medium to away and transmit sound energy from source to other point. Speed of sound waves depends upon medium through which it is ing. It is higher in case of solids and gradually decreases as we move from solids to liquids and gases. b. Another example of mechanical waves is the wave moving through a slinky spring, spring is made of no. of coils and disturbance when initiated at the end of spring moves towards other end displacing coils.

Other common examples of mechanical waves are the waves in a string, water waves etc.

2. Electromagnetic waves: Electromagnetic waves are those waves which do not need any medium at all to propagate from one place to another. They are capable of transmitting energy through vacuum. Examples: Examples of such waves are light waves. These waves require no medium to away. Light waves are electromagnetic fields which alternately change and gives rise to one another in such a way that wave propagates in forward direction.

➢ On the basis of relative motion of particles of medium as wave through 1. Transverse waves: Those waves in which the motion of particles is perpendicular to the direction of propagation of wave are called transverse waves.

Explanation: In this type of wave particles of medium are displaced perpendiculars from their mean position towards extreme position as wave moves forward.

Examples: Examples of transverse waves are the waves produced at the surface of water. When a tip of pencil touches the static water surface it creates some disturbance over its surface. Particles of water are displaced perpendicularly from their mean position as wave proceeds.

2. Longitudinal waves: Those waves in which the motion of particles is parallel to the direction of propagation of wave are called longitudinal waves

Explanation: In these type of waves particles are displaced parallel to the direction of propagation of wave as wave proceeds. Example: Sound waves are longitudinal in nature. Whenever sound wave travels in air particles of medium are displaced parallel to wave propagation direction. They create compressions and rarefactions and propagate the wave.

3. Surface waves: In these type of waves particles of medium move in a circular path. This type of wave is also referred as circular wave because particles of medium undergo motion in a complete circle.

➢ Waves can also be classified according to the no. of dimensions in which they propagate energy. 1. One dimensional wave: Waves propagating energy only in one plane are called one dimensional wave.

Example: Waves moving along spring or a string are one dimensional wave.

2. Two dimensional waves: Waves propagating energy in two dimensions are called two dimensional waves.

Example: Surface waves are dimensional waves.

the

example

of

the

two

Explanation: Ripple produced on surface of water caused by dropping a pebble into a quiet pond is the example of surface waves (two dimensional waves).

3. Three dimensional waves: Waves propagating energy in three dimensions are called three dimensional waves.

Example: a. Sound waves b. Light waves which emanate radially from a small source are 3

dimensional

➢ Waves are also classified according to the shape of wave fronts 1. Plane waves 2. Spherical waves

Explanation: Wavefronts: Wave fronts are the imaginary surfaces at which all the points have same phase of vibration. If the medium is homogenous and isotropic the direction of propagation of wave is always at a right angle to the wavefronts. Ray: A line normal to the wavefronts indicating the direction of motion of waves is called a ray.

1. Plane waves: If the disturbances are propagated in a single direction, the waves are called plane waves. The wavefronts are plane and rays are parallel straight lines. Plane wavefronts are spaced one wavelength apart.

2. Spherical waves: If the disturbance is propagated out in all directions from a point source of waves then it is called as spherical waves. The wavefronts are spheres and rays are radial lines leaving the point source in all directions. Far from the source the spherical wavefronts have very small curvatures and over a limited region they can often be regarded as plane.

➢ Standing/progressive waves One way of classifying the waves is also dividing them in standing or progressive waves.

1. Travelling waves/progressive waves: Disturbance that both varies with time (t) and distance (z). Commonly speaking simple waves that move e.g. on surface of water are travelling waves.

2. Standing waves/stationary waves: Standing waves/stationary waves are a wave that remains in a constant position. Explanation: Usually when two waves travelling in an opposite direction interfere then stationary waves are produced. Usually standing waves are produced by the wave and its reflected wave which comes back from boundary

Note: Some waves are neither purely longitudinal nor transverse. For example in waves on the surface of water particles of water move both up & down, and back & forth as waves move by.

Bibliography (n.d.). Retrieved from www.wikipedia.org: http://en.wikipedia.org/wiki/Wave (n.d.). Retrieved from physics class tutorials: http://www.physicsclassroom.com/Class/waves/u10l1a.cfm (n.d.). Retrieved from http://images.google.com.pk/imgres?imgurl=http://www.urdupages.com/attachmen t.php%3Fattachmentid%3D1970%26stc%3D1%26d%3D1068015818&imgrefurl=htt p://www.urdupages.com/showthread.php%3Ft%3D1772&usg=__AA4ynSDxLvBAOrrF pcdM6Q2zyso=&h=600&w=800&sz=124&hl=en&sta board, p. t. physics XI. punjab text book board. Robert Resnick, D. H. physics (combined edition ed.). john wiley & sons inc.