Current Affairs 8th Class

Category : 8th Class

        Types of Waves

There are normally two types of waves:

(i) Longitudinal wave

(ii) Transverse wave

The nature of the wave depends on the elastic and inertial properties of the medium.

          Longitudinal Waves

It is the wave, in which the particles of the medium vibrates in the direction of propagation of the wave. In this process the particles do not move with the wave, they simply oscillate back and froth about their individual equilibrium position. In the figure given below, the wave is seen as the motion of the compressed region, which moves from left to right. The region in which the particles have high density is called compression and the region in which the particles have low density is called the rarefactions. The distance between any two compressions and rarefactions is called its wavelength.

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            Transverse Waves

The wave, in which the particles of the medium vibrates in the direction perpendicular to the direction of their propagation, is called the transverse waves. The particles do not move along the wave, they simply oscillate up and down about their individual equilibrium position, as the wave passes through the medium.

       There are different types of waves produced by different sources. The wave produced by the home theater is different from that produced by the light of bulb. What is the nature of sound wave produced by the home theater?

(a) Transverse

(b) Plane

(c) Longitudinal

(d) All of these

(e) None of these

Answer: (c)

Explanation

The nature of the sound wave produced by the home theater is longitudinal.

        The wave, which travels in a straight line and cannot bend round the corner is called transverse wave. Which one of the following is an example of transverse wave?

(a) Sound wave

(b) Light

(c) Music

(d) Electromagnetic wave

(e) None of these

Answer: (b)

Explanation

We know that light wave is transverse in nature.

• The total sound energy of 200 pianos is equivalent to the energy needed to light one bulb.
• The speed of sound in steel is 15 times faster than the speed of sound in air.
• The worlds largest and loudest musical instrument is an organ of 33,112 pipes and can produce a sound of 25 brass band and is in Atlantic city USA.
• The animal, which can produce loudest sound in the world is Blue whale. It can produce a sound of 188 dB, which can be picked up from 850 km distance.
• The amount of energy in the tail of electric eels is equivalent to the energy needed to light 12 electric bulbs. The shock from it could kill a person.

• The sound is produced due to the disturbance created in the medium by any source.
• Sound wave is longitudinal in nature and travels in successive compression and rarefactions.
• Sound cannot travel in vacuum.
• The distance between any two consecutive compression or rarefaction and any two crest or trough is called wavelength.
• The time taken for one complete oscillation is called time period.
• To have a distinct sound for hearing, the time interval between the original sound and reflected sound must be at least 0.1 sec.
• The repeated reflection of sound is called reverberation.
• The audible range of hearing for average human is 20 Hz to 20 kHz.
• Ultrasound sound has various appllications in medical science.
• SONAR is used in defense system of the country.