22/06/2017
WAVE
A wave is a disturbance, which propagates energy from one place to the other without the transportation of matter.
Waves are broadly of two types:
Mechanical wave (longitudinal wave and transverse wave)
Electromagnetic wave
Longitudinal Waves
In this wave the particles of the medium vibrate in the direction of propagation of wave.
Waves on springs or sound waves in air are examples of longitudinal waves.
Transverse Waves
In this wave the particles of the medium vibrate perpendicular to the direction of propagation of wave.
Waves on strings under tension, waves on the surface of water are the examples of transverse waves.
Electromagnetic Waves
The waves, which do not require medium for their propagation i.e., which can propagate even through the vacuum are called electromagnetic waves.
Light radio waves, X-rays etc are the examples of electromagnetic wave. These waves propagate with the velocity of light in vacuum.
Sound Waves
Sound waves are longitudinal mechanical waves. Eased on their frequency range sound waves are divided into following categories.
The sound waves which lie in the frequency range 20 Hz to 20000 Hz are called audible waves.
The sound waves having frequencies less than 20 Hz are called infrasonic
The sound waves having frequencies greater than 20000 Hz are called ultrasonic waves.
Ultrasonic waves are used for sending signals, measuring the depth of see, cleaning clothes and machinery parts, remaining lamp short from chimney of factories and in ultrasonography.
Speed of Sound
Speed of sound is maximum in solids minimum in gases.
When sound goes from one medium to another medium, its speed and wave length changes, but frequency remain unchanged. The speed of sound remains unchanged by the increase or decrease of pressure.
The speed of sound increases with the increase of temperature of the medium.
The speed of sound is more in humid air than in dry air because the density of humid air is less than the density.
Echo: The repetition of sound due to reflection of sound waves is called an echo.
Intensity: It is defined as amount of energy passing normally per unit area held around that point per source unit time.
Pitch: The sensation of a frequency is commonly referred to as the pitch of a sound.
Sonar: It stands for sound navigation and ranging. It is used to measure the depth of a sea, to locate the enemy submarines and shipwrecks.
Doppler's Effect
If there is a relative motion between source of sound and observer, the apparent frequency of sound heard by the observer is different from the actual frequency of sound emitted by the source. 1 his phenomenon is called Doppler's Effect.
