WAVE MOTION & SOUND -1
WAVE:-
Is a disturbance by which energy is transferred from one point to the other through vibrations of the medium particles without their actual movements
WAVE MOTION :-
the movement of disturbance produced in one part of medium to another involving the transfer of energy but not the transfer of matter.
Examples:
1) ripples on water surface
2) propagation of sound wave through a medium
Explanation Of Wave Motion
If we drop a stone in to a pond we see circular water waves spreading in all directions on the surface of water
The disturbance moves from one place to another but the water is not carried with it.
The material in which the wave motion is produced is called a medium.
when the stone is thrown in to the pond , the energy carried by stone disturbs the water molecules closed to it.
Water molecules near the stone gains energy starts vibrating up and down.
Vibrating Water molecules transfer some of the energy to the next set of water molecules.
In this way water wave is formed
Characteristics of wave motion
1) parto of the medium vibrates about their mean position. Particles of the medium don't move from one place to another
2) there is no transfer of matter through the medium the energy is transferred from one point of the medium to another
3) during wave motion, medium doesn't move the disturbance travells through the medium
4) wave motion travells with same speed in all directions, speed of wave depends on nature of medium
PULSE:
Wave setup by a single disturbance in the medium is called pulse
Classification of waves:
1) based on necessity of medium
i) Mechanical waves
ii) Electro magnetic waves
i) Mechanical waves
The wave which required material media for their transmission is called mechanical wave
Example:
vibrations in stretched string, surface of water
Sound waves in air
ii) Electro magnetic waves
The wave which do not required material media for their transmission is called mechanical wave
Electro magnetic waves can travel through vacuum with the speed of light ( 3x10⁸ m/s)
Example:
Light waves
X- rays
Gamma rays
Radio waves
Micro waves.
2) based on propagation of wave
i) longitudinal wave
ii) transverse waves
i) longitudinal wave
A wave in which the particle of the medium vibrates up and parallel to the direction of wave
Example:
Sound waves in air
Wave in spiral spring
Wave produced in air when a sitar is plucked
Representation of longitudinal wave:
In the following figure the particle of the mediums vibrates back and forth in the horizontal direction.
Compression and Rarefactions of a longitudinal wave:
Compression:
The part of the longitudinal wave in which the density of the particles of the medium is higher than the normal density is called a compression.
Rarefaction:
The part of the longitudinal wave in which the density of the particles of the medium is lesser than the normal density is called a Rarefactions
Wave length: (λ)
The distance between two successive compressions or between two successive Rarefactions is equal to one wave length.
ii) Transverse wave:
A wave in which the particle of the medium vibrates up and perpendicular to the direction of wave
Example:
waves on surface of water
Wave on long stretched rubber tube
Waves on long stretched string
Light waves & radio waves
Representation of Transverse wave:
The direction of wave is from A to B but the vibration of particles are along CD which is right angle to the direction of wave.
Crest:
The elevation or hump in transverse wave is called through.
Through:
The depression or hollow in a transverse wave is called through
Wavelength:
the distance between the two consecutive crests or between two consecutive troughs is equal to one wavelength.
Note:
1) Distance between crest and adjacent trough is λ/2
2) transverse wave can not travel inside the liquid and in gases
3) propagation of transverse wave through a medium results in the formation of crest and trough.
Difference between transverse waves and longitudinal waves:
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