Synopsis On Wave

SYNOPSIS on WAVE-MOTION and SOUND • • •

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Periodic motion- The motion which repeat itself in equal interval of time. Vibratory motion- The to and fro motion of an object about its mean position. Motion under elastic restoring force- The type of motion occurs when the force acting on a body is directly proportional to the displacement and directed towards the mean position; i.e. F= -kx where negative sign shows that the direction of forces acting on a body attached to a helical spring is always opposite to the direction of displacement ‘x’. During vibratory motion the K.E is maximum at mean position and is zero at extreme position. During vibratory motion the P.E is zero at mean position and maximum at extreme position. During vibratory motion body possesses inertia. Displacement- It is the least distance b/w two points in specified direction. Amplitude- It is the maximum displacement of the body on either side of its equilibrium position. Time period- Time required to complete one vibration. Frequency- Number of vibrations in one second. It is the reciprocal of time period f=1/T its unit is Hertz (Hz) or Cycles/second. Simple pendulum- a simple pendulum consists of a single isolated particle suspended from a frictionless support by a light inextensible string. The time period of simple pendulum is T= 2π l / g Where’l’ is the length of pendulum and ‘g’ is acceleration due to gravity Second’s pendulum- The pendulum which takes two second to complete one vibration Waves- The periodic disturbance of particle in any medium is called waves. Mechanical waves- The type of waves that required medium for their propagation for e.g. sound waves, waves on the surface of water & waves along a string. Electromagnetic waves- The type of waves that do not required medium for their propagation for e.g. light waves ,radio waves, microwaves, infrared waves, X-rays gamma rays. Types of Mechanical waves: Longitudinal waves- The waves in which particles of the medium vibrate along the direction of propagation. Transverse waves- The type of waves in which particles of the medium vibrates perpendicular to the direction of propagation. Resonance- it is defined as the specific response of a system, which is able to oscillate with a certain period to an external force with the same period. Relation b/w wave velocity, frequency and wavelength- v = f λ Speed of sound increases with temperature by the formula: vt = v0 T / 273 Characteristics of musical sound- Intensity, loudness, pitch, timber(quality).

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Echo: the reflection of sound in 1/10th of a second is called echo.