Tuesday, October 16, 2012

CBSE Physics help class 8 Chapter: Sound

CBSE Physics help class 8 Chapter: Sound

What is the difference between noise and music?

Unpleasant sounds are called noise whereas music is a sound, which produces pleasant sensation. But, if the musical sound is too loud, it becomes noise.

What is eardrum? How does it play an important role in hearing?

A thin tightly stretched membrane t is called eardrum. it vibrates sound wave and sends vibrations to the inner ear.

Which property of vibrations determines the pitch of the sound? Explain giving some examples.

The frequency determines the shrillness or pitch of a sound. If the frequency of vibration is higher the sound has a higher pitch. If the frequency of vibration is lower, the sound has a lower pitch. Women sound is shriller than man due to high frequencies

What is the audible range of frequencies for human beings?

The range of audible frequencies is roughly between 20 to 20,000 Hz.

Dogs can hear frequencies up to 40,000 Hz while cats can produce and hear frequencies up to 70,000 Hz.

What is noise pollution? What are its major causes?

Presence of excessive or unwanted sounds due to irregular frequencies in the atmosphere is called noise 
pollution.

Major causes of noise pollution are sounds of vehicles, explosions including bursting of crackers, machines, 
loudspeakers etc.

How can the noise pollution be controlled in a residential area?

Noise producing industries should be set up away of such areas. Use of automobile horns be minimized. TV and music systems should be run at lower volumes. Plants must be planted along the roads and around buildings to minimize the harmful effects of noise pollution.

What are the harms of noise pollution?

Lack of sleep, high blood pressure, anxiety and many more health disorders are  caused by noise pollution. if a  person is exposed to a loud sound continuously may get temporary or even permanent deafness.

How does the loudness of sound depend upon the amplitude?

Loudness of sound is proportional to the square of the amplitude of vibration producing the sound. For example, if the amplitude becomes twice the loudness increases 4 times.

Why a tabla with tight membrane does vibrates at a higher pitch than a tabla with a loose membrane?

A tight membrane vibrates at a much higher frequency than a loose one, so that the sound produced with 
tight membrane has a higher pitch.

Give some applications of ultrasound?

To detect flaws in metals and structures in industries

 To test the thickness of outer parts in industries

As a diagnostic tool in medical science 

In relieving pain, in joints and muscles in medical science

What is pitch of the sound?

It is characteristic of sound depending upon its frequency. Different frequencies produce different pitch of 
sound.

What is called musical sound?

 Sound is defined as sensation of hearing. Musical sound is one which gives a pleasant sensation to mind.

What are radio waves?

The types of waves which needed no medium to travel is called radio waves or Electromagnetic wave

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