Characteristics of Sound wave
Characteristics of Sound wave:
When a wave passes through a medium, there is a temporary displacement of the particles of the medium from their actual positions. The maximum displacement of these particles of the medium from their actual positions when a wave passes through them can be defined as the amplitude of the wave. In other words, it is used to describe the size of the wave. It is measured in ‘meter' in the S.I. unit.
Wavelength is the minimum distance in which the sound wave repeats itself. It is the length of one complete wave. In a sound wave, the combined length of an adjacent rarefaction and compression is known as the wavelength. It is also important to remember that the distance between the centres of two successive rarefactions and two successive compressions is equivalent to its wavelength. The S.I. unit of wavelength is also metre.
The time that is required to produce one complete wave or cycle is known as the period of the wave. One full vibration of the vibrating body produces one complete wave. So, the time taken for completing one vibration can be referred to as the period. The Period is denoted by the letter T and the unit of measurement is second (S).
The total number of the cycles or waves that are produced in one second can be referred to as the frequency of the wave. Alternatively, frequency can also be defined as the number of vibrations per second. For instance, if 20 vibrations are produced in one second then the frequency of the waves will be 10 Hertz and 10 cycles. The frequency of a wave is fixed and it does not change when it passes through different medium. The unit of frequency is Hertz or Hz.
The distance that is covered or travelled by a wave in one second is regarded as the velocity (speed having a direction vector) of the wave. The unit of measurement of velocity is meters per second. The velocity of a wave can be found by dividing the distance travelled with the time taken. It can also be found by multiplying the frequency of the wave with the wavelength.
When an object travels in the air with a speed greater than that of the sound, it produces a sound with high energy. This energy is loud enough that it can break glasses or damage the buildings. The sound produced is similar to the sound of an explosion or thunderclap.
These objects exert a large amount of pressure on the air which causes the production of shock waves in the air. These shock waves produce extremely large and loud sound waves which are called Sonic booms.
Speed of light in air = 3 * 108 m/s
Speed of sound in air = 333 m/s
This clearly states that sound travels a lower speed than that of light in air. This is a reason why at the time of lightening, the light is visible instantly while the sound of the thunder reaches our ears after a few seconds.
Sound can bounce off a solid or a liquid. Some materials like metals and walls are called Good Reflectors of Sound as they do not absorb the sound while others like clothes and sponge are called Bad Reflectors of Sound as they absorb the sound easily.
Laws of Reflection of Sound
The incident sound wave, the reflected sound wave and the normal, all lie in the same plane.
The angle of incident of incident sound wave is equal to the angle of reflection formed by the reflected sound wave, that is, i = r