Waves

The wave is a form of disturbance which transmits energy from one place to another without the actual flow of matter as a whole. Waves are of three types: Mechanical waves, Electro Magnetic waves, matter waves. Water waves or sound waves are called mechanical or elastic waves as they require a material medium for their propagation. A material possesses both elasticity as well as inertial. Light waves don’t require any material medium for their propagation. Light waves are electromagnetic or non-mechanical waves which can propagate through vacuum. Matter waves are associated with moving electrons, protons, neutrons and other fundamental particles and even atoms and molecules. The matter is constituted and other fundamental particles and even atoms and molecules. The matter is constituted by electrons, protons, and neutrons and other fundamental particles. The waves associated with matter particles are called matter waves. Matter waves arise in quantum mechanical description of nature. Wave motion in a form of disturbance which is due to the repeated periodic vibrations of the particles of the medium about their means positions. The motion is handed over form one medium particle to another without any net transport of the medium during wave motion. Mechanical waves are of two types i.e. transverse waves and longitudinal waves. A wave is said to be progressive or travelling waves if it travels from one point of the medium to another. The waves on the surface of water are of two types: capillary waves and gravity waves. The restoring force that produces gravity waves is the pull of gravity which tends to keep the water surface as its lowest level. The oscillation of the particles in gravity waves is not confined to the surface only, but extends with diminishing amplitude to the very bottom. The particle motion in water waves involves a complicated motion, they are not only moving up and down but also back and forth. The waves in an ocean are a combination of both longitudinal and transverse waves. Transverse and longitudinal waves travel with different speeds in the same medium. “k” is called the propagation constant or angular wave number. S.I unit of “k” is radian (rad) per meter.
Sound waves are mechanical waves which can’t propagate in vacuum. The speed of sound does not depend on the frequency or wave length. Sound waves can’t travel in saw dust or dry sand because the medium is not continuous. The damping of sound in wood is much larger as compared to that in metals. Higher the frequency of sound greater is the pitch of sound. The voice of ladies and children is of higher pitch than that of men. The sound is reflected and refracted according to the same laws as light does. The wave length for ultrasonic is very small, therefore they are not diffracted by ordinary objects or holes etc. The speed of mechanical waves is determined by the properties of the medium i.e. elasticity and inertia and not by the nature, intensity, amplitude or shape of the wave. Velocity of sound is largest in hydrogen among gasses. Monosyllabic sound is produced in about 0.2 s. The vibration of the prongs of a tuning fork is the transverse and that of the stem are longitudinal. The point where stem of a tuning fork is connected to the prongs is antinodes. The end of the prongs is also antinodes. There is node between them which is nearer to the stem than the ends of the prongs. The speed of sound in the air is not affected by the changes in pressure. For every 1⁰C rise in temperature, the speed of sound increases by 0.61 meter per sec. Due to change in temperature, the wavelength of sound waves is affected. Beats are not audible if beat frequency is more than 10Hz. If the prong of a tuning fork is loaded near the stem its frequency increases and when it is filled near the stem, the frequency decreases. The number of beats produced per second is equal to the difference in the frequencies of the superposing notes. In the progressive waves, the crest and troughs or compressions and rarefactions move with the speed of the wave. When there is no relative motion between the source and listener, the Doppler’s effects is not observed. When a source of sound moves, it cause change in wavelength of the sound received by the listener. If source and listener move in a mutually perpendicular direction no Doppler’s effect is observed.

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By teenstudents Posted in Biology

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