Want to learn by Video Lectures? Similarly, in an electric Class 10th Physics Ncert Book Zip bell, when connected to electricity starts producing sound. Here, again electrical energy is converted into Class 10th Physics Ncert Book List sound energy. Activity to show that vibrating bodies produces sound: - Strike the prongs of a tuning fork on a rubber pad and bring it near the ear.
We can hear a sound. If a suspended table tennis ball is touched with the vibrating prong, the ball is pushed away repeatedly. This shows that the prong is vibrating and vibrating objects produces sound. In every musical instrument, there is a vibrating part which produces sound. In case of musical instruments like flute, the air column vibrates to produce sound. In stringed musical instruments like sitar, veena etc, there is a tightly stretched string which vibrates to produce sound.
In humans, sound is produced by the voice box or the Larynx. Vocal cords in the larynx vibrate and produce sound. We hear sound with our ears. Suspend an electric bell in an air tight bell jar.
Connect the bell jar to a vacuum pump. If the switch is pressed, we can hear the sound of the bell. If air is pumped out through the vacuum pump, we cannot hear the sound of the bell. This shows that sound needs a medium to travel and sound cannot travel in vacuum. The particles of sound wave do not move from one place to another. They just oscillate back n forth about their position of rest. The disturbance is carried forward.
Hence, sound waves are longitudinal waves. Hold one end of the sling key n fix the other end to the wall nail. Now, stretch sling key by pulling the hand, after a while push the stretched sling key towards the wall. Amplitude depends upon the force with which an object vibrates.
Similarly, if we hit the table slowly, the sound produced is low as its amplitude is small. Thus, loudness as well as soft sound is determined by its amplitude. Its SI unit is metre. We can calculate the frequency of sound by calculating the number of compressions or rarefaction in one second. It is represented by a Greek letter Greek letter nu.
SI unit is Hertz. SI unit is named after Heinrich Rudolph Hertz who laid foundation 4 future development of radio, telephone, telegraph n TV. Time period of a sound wave is the time between 2 successive compressions or 2 successive rarefactions. The velocity of sound remains almost same for all frequencies in a given medium under the same physical conditions.
The speed of sound also depends on the temperature of the medium. If the temperature of the medium is more, the speed of sound is more. Loudness or softness of a sound wave is the sensation that depends upon its amplitude.
But, when we strike the top of a table with lesser force, the vibrating table top produces soft sound waves. Louder sound has more amplitude. The difference is due to one more characteristic of sound namely pitch. The pitch of sound shrillness or flatness depends on the frequency of vibration.
Faster the vibration of the source, higher is the frequency and higher the pitch and vice versa. Similarly, low pitch sound corresponds to low pitch. Many objects such as aircrafts, bullets, rocket planes travel at speeds greater than the speed of sound in air. Such objects are said to be travelling with supersonic speed.
Sonic boom is the loud sound due to shock waves generated by objects moving with supersonic speed. Shock waves have lot of energy, they can damage buildings and break glasses. But, only important here is that the sound wave needs rough or polished and large obstacle is very much necessary. We require 2 identical pipes made up of chart paper,a clock, table and a scale and protractor. Take two pipes of the same length and arrange them on a table near a wall or metal plate.
Keep a clock near the open end of one pipe and try to hear the sound of the clock through the other pipe by adjusting the position of the pipe. Now measure the angles of incidence and reflection. Then lift the second pipe and try to hear the sound. It will be seen that the angle of incidence is equal to the angle of reflection.
The incident ray, the reflected ray and normal all lie in the same plane. R eflection of sound is used in many devices. For example; megaphone, loudspeaker, bulb horn, stethoscope, hearing aid, sound board etc.
Megaphones, horns, musical instruments like trumpets, shehnais etc. Doctors listen to sounds from the human body through a stethoscope. Generally the ceilings of cinema halls and auditoriums are curved so that sound after multiple reflections reaches all parts of the hall.
It also depends on temperature. Echoes may be heard more than once due to repeated or multiple reflections of sound from several reflecting surfaces. Persistence of sound wave for a long time because of repeated multiple reflections of sound is called reverberation. Usually, this happens in big halls. Sound becomes too blurred and distorted to be heard in big concert halls because of reverberation. This can often lead to annoyance. Reverberation can be prevented by stopping the reflection of sound.
This could be done by using soft sound absorbent materials, Class 10th Ncert Physics Book Ed such as curtains, plant fibre, compressed fireboard, carpets, etc. These materials absorb undesired reflected sound and reduce reverberation. The human ear can hear the sound between frequencies of 20 Hz to 20, Hz. Thus, audible range or range of hearing for an average human being is between 20 Hz to 20, Hz. However, children under 5 years of age can hear the sound upto Hz. Sound, below the frequency of 20Hz is called infrasonic or infrasound.
Infrasound is produced because of very slow vibration. For example; simple pendulum produces sound below 20Hz. Human being cannot hear infrasound as their ears are not adapted to hear the sound of such range. Many animals such as whale, elephant, rhinoceros, etc. Ultrasound or ultrasonic sound:- Sound, above the frequency of Hz is called ultrasound. Humans cannot hear the ultrasonic sound. However, many animals such as dogs, cat, bat, monkey, deer, etc.
Human children can also hear to ultrasound. Earthquakes, volcanic eruptions also produce ultrasound. Ultrasound is sound waves of high frequency. Because of high frequency, ultrasound is associated with more energy and can penetrate upto a large extent. This characteristic of ultrasound makes it very useful for many purposes. Some of its uses are given here:. The human ear can be divided into three main parts, viz.
Outer Ear: The outer ear is outside the body and is also called pinna. It extends into the ear canal. Ear canal is filled with air. Middle Ear: The middle ear is composed of the ear drum or tympanum it is an elastic membrane, circular in shape and the bone ossicles. There are three bone ossicles, namely, the hammer, the anvil and the strirrup.
The cochlea is filled with liquid. The cochlea makes the hearing apparatus and the auditory nerve from it goes to the brain. Working of Human Ear: The outer ear called pinna collects the sound waves. The sound waves passes through the ear canal to a thin membrane called eardrum.
The eardrum vibrates. The vibrations are amplified by the three bones of the middle ear called hammer, anvil and stirrup. The middle ear then transmits the sound waves Class 10th Physics Ncert Book Day to the inner ear.
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