Waves are present everywhere. Whether we recognize it or not, we encounter waves on a daily basis. We experience a variety of waves on daily basis including sound waves, radio waves, microwaves, water waves, visible light waves, sine waves, stadium waves, earthquake waves, cosine waves and waves on a string. Besides these waves we also experience various other motions which are similar to those of waves and are better referred as wavelike. These phenomena include the motion of a pendulum, the motion of a mass suspended by a spring and the motion of a child on a swing. Wave phenomena emerge in unexpected contexts. The flow of traffic along a road can support a variety of wave-like disturbances as anybody who has experienced a slowly moving traffic will know. The beat of your heart is regulated by spiral waves of chemical activity that swirl across its surface. You control the movement of your body through the action of electrochemical waves in your nervous system. Finally, quantum physics has revealed that, on a small enough scale, everything around us can only be described in terms of waves. The universe isn’t really mechanical in nature. It’s made of fields of force. When a radio antenna makes a disturbance in the electric and magnetic fields, those disturbances travel outward like ripples of water in a pond. In other words, waves are fundamental to the way the universe works.
Wave motion is a mode of transmission of energy through a medium in the form of a disturbance. It is due to the repeated periodic motion of the particles of the medium about an equilibrium position transferring the energy from one particle to another.
The waves are of three types - mechanical, electromagnetic and matter waves. Mechanical waves can be produced only in media
which possess elasticity and inertia. Water waves, sound waves and seismic waves are common examples of this type. Electromagnetic waves do not require any material medium for propagation. Radio waves, microwaves, infrared rays, visible light, the ultraviolet rays, X rays and γ rays are electromagnetic waves. The waves associated with particles like electrons, protons and fundamental particles in motion are matter waves.
Waves on Surface of Water
In order to understand the concept of wave motion, let us drop a stone in a trough of water. We find that small circular waves seem to originate from the point where the stone touches the surface of water. These waves spread out in all directions. It appears as if water moves away from that point. If a piece of paper is placed on the water surface, it will be observed that the piece of paper moves up and down, when the waves pass through it. This shows that the waves are formed due to the
vibratory motion of the water particles, about their mean position.
Wave motion is a form of disturbance which travels through a medium due to the repeated periodic motion of the particles of the medium about their mean position. The motion is transferred continuously from one particle to its neighbouring particle.
Characteristics of Wave Motion
(a) Wave motion is a form of disturbance travelling in the medium due to the periodic motion of the particles about their mean position.
(b) It is necessary that the medium should possess elasticity and inertia.
(c) All the particles of the medium do not receive the disturbance at the same instant (i.e) each particle begins to vibrate a little later than its predecessor.
(d) The wave velocity is different from the particle velocity. The velocity of a wave is constant for a given medium, whereas the velocity of the particles goes on changing and it becomes maximum in their mean position and zero in their extreme positions.
(e) During the propagation of wave motion, there is transfer of energy from one particle to another without any actual transfer of the particles of the medium.
(f) The waves undergo reflection, refraction, diffraction and interference.
 
Amplitude is the height of the wave, measured in meters.
Wavelength is the distance between adjacent crests, measured in meters.
Period is the time it takes for one complete wave to pass a given point, measured in seconds.
Frequency isthe number of complete waves that pass a point in one second, measured in inverse seconds, or Hertz (Hz).
Speed is the horizontal speed of a point on a wave as it propagates, measured in meters / second.
The direction a wave propagates is perpendicular to the direction it oscillates for transverse waves.
For electromagnetic wave, propagation may occur in a vacuum as well as in a material medium.
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Question 1
Which of the following statements is wrong
(a) Sound travels in a straight line
(b) Sound travels as waves
(c) Sound is a from of energy
(d) Sound travels faster in vacuum that then in air
Question 2
When a compression is incident on rigid wall it is reflected as,
(a) Compression with a phase change of p
(b) Compression with no phase change
(c) Rarefaction with a phase change of p
(d) Rarefaction with no phase change
Question 3
In the longitudinal waves the direction of vibration in medium of particle is,
(a) Perpendicular to propagation of wave
(b) Parallel to propagation
(c) Different from each other
(d) Variable for time to time.
Question 4
The relation between frequency n, wavelength l and velocity n of a wave is,
(a) n = nl
(b) n = nl
(c)
(d)
Question 5
With the propagation of a longitudinal wave through a material medium the quantities transmitted in the propagation direction are,
(a) Energy, momentum and mass
(b) Energy
(d) Energy and linear momentum
| Q.1 | Q.2 | Q.3 | Q.4 | Q.5 |
d
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