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Waves, ➢ A wave is a disturbance in a medium that transports energy without causing, net particle movement., ➢ Wave is defined as the disturbance which transfer energy from one location to, another without transfer of mass, particle, and medium., , Characteristics of Wave, Waves include the following characteristics:, ➢ The particles of the medium traversed by a wave vibrate only slightly about, their mean positions, but they are not permanently displaced in the wave’s, propagation direction., ➢ Along with or perpendicular to the wave’s line of travel, each succeeding, particle of the medium performs a motion quite identical to its predecessors., ➢ During wave motion, only energy is transferred, but not a piece of the, medium., ➢ In wave motion each particle receives disturbance latter than its preceding, particle., ➢ In any medium the wave velocity remains constant, while the particle velocity, changes about its mean position, ➢ The velocity with which the wave travels is different from the velocity with, which particle oscillate., ➢ There is a regular phase difference between the particles of the medium, because each particle receives disturbance little later than its preceding, particle., , Some terminologies in Wave -:, 1. Amplitude -: The maximum displacement through which an oscillating, particle of the medium undergoes on either side of its equilibrium position is, called the amplitude. It is represented by ‘a’
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2. Time-period -: The time taken by the medium particle in completing one, oscillation is called the time-period. It is denoted by ‘T’., 3. Frequency -: The number of oscillations made by a medium particle in 1 second, is called Frequency. It is denoted by ‘n’ or ‘f’. the S.I unit of frequency is hertz., 1, n=, T, 4. Phase -: The phase of an oscillating particle at any instant denotes the position, and direction of motion of the particle at that instant., 5. Wavelength -: The distance moved by the wave in the time of one complete, oscillation of a particle of the medium is called the wavelength., OR, The distance between two nearest medium particle oscillating in the same phase, is called wavelength. It is denoted by λ., , 6. Wave Speed –: The distance traversed by a wave in 1 second is called the wave, speed. It is denoted by ‘v’., 7. Wave Number -: The number of waves present in a unit distance of the medium, is called the wave number. It is equal to the reciprocal of the wavelength., , 8. Angular Wave Number or Propagation Constant -: the quantity 2𝜋⁄λ is called, angular wave number or propagation constant of a wave. It is denoted by k., the S.I unit of k is rad/m, 9. Wave Velocity -: The distance covered by a wave per unit time in its direction, of propagation is called its wave velocity. It is also denoted by ‘v’., ❖ Relation Between Frequency, Wave speed and Wavelength -:, Let assume ‘n’ be the frequency and ‘T’ the time-period of an oscillating body. So the, wave produced by this body will travel a distance of λ in a time T, where distance, travelled by wave is its wavelength. Thus,, Distance travelled in T second = λ, λ, , Distance travelled in 1 second = T, But as we know that distance travelled in 1 second by the wave is its wave speed., Therefore,, λ, , v=T
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v = nλ, speed = frequency × wavelength, Q.1 In a specific medium, a wave travels at 900 meters per second. Calculate the, wavelength of a specific point in the medium if 3000 waves pass through it in 2, minutes., Q2. The speed of a wave in a medium is 960m/s. if 3600 waves are passing through a, point in the medium in 1 minute, then calculate the wavelength., Q3. What is the frequency of radio waves transmitted by a station, if the wavelength, of these waves is 300 m ?, Q4. A hospital uses an ultrasonic scanner to locate tumour in a tissue. What is the, wavelength of sound in the tissue in which the speed of sound is 1.7 km/s? the, operating frequency of the scanner is 4.2MHz., Q5. A wave of frequency 250 Hz travels with a speed of 4800 m/s in iron. (i) what will, be its wavelength in iron? (ii) what will be its wavelength in air if its speed in air is 332, m/s., Q6. The frequency of a radio transmission centre is 30 MHz . What is the wavelength, of the waves transmitted from the station., , ❖ TYPES OF WAVE
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1. Mechanical wave -:, , •, •, •, •, , A mechanical wave is a wave that is an oscillation of matter, and therefore transfers energy, through a medium., A mechanical wave is a wave that is not capable of transmitting its energy through a, vacuum., Mechanical waves require a medium in order to transport their energy from one, location to another., Examples of Mechanical Waves are Sound Waves, Spring Waves, Stadium Waves,, Jump Rope Waves.
