Wave motion & Sound- Waves/ Types of waves?

@sudhanshunath January 09, 2021

Wave motion and sound

 Contents

    1:- What is a wave 
    2:- Types of wave 
    3:- Transverse Wave
    4:- Longitudinal  wave
    5:- Terms related to wave 
    6:- Wave Interactions 

Wave 
     A wave is any disturbance that transmits energy through matter or empty space. A few examples of wave are water waves in the ocean, light waves from the sun, radio waves transmitted to the radio, micro wave inside the micro oven and sound waves from the telephone. 
  The material through which the wave travels dies not move forward with the energy. 
 Most waves transfer energy by the vibration of particles in a medium. 

Types of Wave 
  • Waves that need a medium are called mechanical waves. Seismic waves caused by earthquake travel through Earth's crust. They are mechanical waves. 
  • Some waves like light waves which can trasfer energy without going through a medium are called electromagnetic waves. 
  • All waves transfer energy by repeated vibrations. Waves can be classified based on the direction in which the particle if the medium vibrate compared with the direction in which waves move: 
the two main types of waves are 
   1:- Transverse Waves &
   2:-  Longitudinal Waves

 Transverse Waves:-
        Transverse wave is a wave in which the particle of the medium move perpendicularly to the direction, the wave is travelling. A wave moving on a rope is an example of a transverse wave. 
 The highest point of a transverse wave is called a crest 
 the lowest point between each crest is called trough. 

 Longitudinal Wave
        In a longitudinal wave, the particle of the medium vibrate parallel to the direction of wave motion. Longitudinal waves are formed when the end of a spring is pushed. 
   When the end of a spring is pushed, the coils of the spring crowd together and when the end of the spring is pulled back, the coils are also pulled apart. A part of a longitudinal wave where the particles are crowded together is called a compression and  a part where the particles are spread apart is a rarefaction. 
Compressions and Rarefactions are like the crest and troughs of a transverse wave as shown in the figure below. 
A) Longitudinal Wave
B) Transverse Wave   



5:- Terms Related to Wave
     
      a) :- Oscillation :- The to and fro motion when one full wave is constituted is called one oscillation. A wave  starting from A and travelling up to C constitutes one oscillation. 
  
      b):- Wavelength:- A wavelength is the distance between any two consecutive crests or compressions in a wave. The distance between two consecutive troughs or Rarefactions is also a wavelength. In fact, the wavelength is the distance from any point on a wave to an identical point in the wave. It is the wave. It is the distance moved by the wave in one complete oscillation.
 It's unit is or m. 
If you shale a rope rapidly the waves will be of shorter wavelength with more energy imparted to the waves you shake the rope slowly. 
    Shorter wavelength→ more energy 
    Longer wavelength→ less energy

     c):- Amplitude:- The amplitude of a wave is related to it's height  it is the maximum displacement of a wave on either side of its mean position. 
A wave with a large amplitude carries more energy than the energy carried by a wave with amplitude: thus, shaking a rope, it requires a greater force to create a wave with  large amplitude. 

     d):- Time period :- The time taken by a wave to complete one oscillation is known as it's time period. It is denoted by T and 
it's unit is second. 
 
    e):- Frequency :- The number of waves i.e., the number of oscillation made by a wave in one second is known as it's frequency. 
 It is denoted by later 'f' or 'n'. 
The unit of frequency is hertz (Hz). 
 
     f)- Wave speed :- Wave speed is the speed at which a wave travels. It can be calculated by using wavelength and frequency. 
Thus,  wave speed is denoted by v, then
Equation:- 
wave speed = wavelength × frequency

Relationship between
Frequency and Wavelength 

    The wave equation indicates the relationship between frequency and wavelength. If a wave is travelling at a certain speed and it's frequency is doubled then it's wavelength will be halved of if the frequency is halved, then the wavelength would be doubled. 
 We can say that 
 Frequency and wavelength are inversely related. 
    


6:- Wave Interactions 
       
   a)- Reflection :- It happens when a wave bounces back after hitting a barrier. 

   b):-  Refraction:- It is the bending of a wave as the wave passes from one medium to another medium at an angle is called refraction. 
 When a wave moves from one medium to another, the wave's speed changes. When a wave enters a new medium, the wave changes wavelength as well as speed. As a result, the wave bends and travels in  a nee direction. (Frequency remains unchanged). 
 
  c)- Diffraction :- The bending of waves around a barrier or through an opening is known as diffraction. The amount of diffraction depends on its wavelength and the size of the barrier or opening the wave encounters. 
A person can hear music around the corner of a building because sound waves long wavelength and are able to diffract around corners. However, he cannot see who is playing the music because the wavelength of light waves are much shorter than sound waves, so light is not diffracted very much. 
  
  d) Interference :- the result of two or more waves overlapping is called Interference. 
 
  e) Resonance:- A phenomenon that occurs when two objects naturally vibrate at same frequency; the sound produced by one object causes the other object or vibrate. 

       
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