Wave Motion

Amplitude: The amplitude of a wave is defined as the maximum displacement or deflection of the particle in the direction perpendicular to the direction of wave motion.

Hence amplitude = 1.5m.

Speed: The speed is determined as the distance d travelled by an object in time t.

According to question: d = 800 m

t = 2 s

hence, speed

= 400 m⁄s

Frequency: It is defined as the rate of vibration constituting a wave or time taken by the number of vibration. That is mathematically it is the reciprocal of the time period of the one complete vibration of the wave.

S.I. unit = hertz

Formula used:

also, we know that speed = wavelength × frequency

⇒ wavelength = 4 m {from the figure, because one complete cycle = wavelength, as shown below:)

Acoustics of buildings-It is the part of the engineering science which study or deals about problems or factors for the clear audibility of the buildings.

Four steps to avoid problems caused by multiple reflection:-

•Use of sound absorbing material for the construction of the building.

•Tight packing of the building for cancellation of the outer noise.

•Make the floor of the building/hall rough.

•The design of the ceiling matter the most, if one want to increase multiple reflection the ceiling should be curved while for less reflection ceilings should be flat.

Info. from the question:

Speed of sound = 1500 m⁄s

Time taken for to and fro round = 4 s

The time given in the question is of complete round of sound wave that is sending and receiving it back, so if we take distance between ship and rock = d then,

the total distance travelled = 2d

2d = speed× time

2d = 1500× 4

2d = 6000

d = 3000 m.[T1]

Hence, the distance between rock and ship = 3000 m.

Resonance is a stage of forced oscillation when the vibrating body drives another body to oscillate with greater amplitude at specific frequency.

As you excite a tuning fork of frequency 512Hz and raise the inner column simultaneously you will observe increase in the loudness of the sound because when frequency of the air column and fork are equal then there will be maximum sound produced as they will be in resonance.

When I visited a nearby cinema theatre, I observed the following things:

•The ceiling of the theatre was in curved shape for the multiple reflection, so that everyone can hear the sound of the movie. As a curved ceiling results in the multiple reflection.

•The floor of the hall was little rough or the carpet used was not smooth, because after multiple reflection the sound need to be absorbed, if it is not absorbed it will mix up and will create a tragic with the next sound.

•The sound boards behind the screen was curved for multiple reflection so that everyone can hear the sound.

In the veena, the string is attached to the sound box of the veena, the vibrating string is capable of forcing the sound box into vibrating at that same natural frequency. The sound box in turn forces air particles inside the box into vibrational motion at the same natural frequency as the string. The entire system (string, veena, and enclosed air) begins vibrating and forces surrounding air particles into vibrational motion.

Hence the tendency of one object to force another adjoining or interconnected object into vibration motion is referred to as a forced vibration.

In the case of the veena, string is mounted to the sound box, the fact that the surface area of the sound box is greater than the surface area of the string means that more surrounding air particles will be forced into vibration. This causes an increase in the amplitude and thus loudness of the sound.