Science Do as directed; [1 M ]

Sound is a mechanical wave and hence it needs a medium to propagate and the outer space has vacuum and therefore if a bomb explodes on the moon its sound will never reach the Earth.

Supersonic aircrafts.

Vacuum.

When sound travels from one medium to another, both its velocity and wavelength undergo changes. Thus, if the velocity of sound doubles when it travels from one medium to another, its wavelength also doubles. The frequency of sound depends upon the source of sound, not the medium of propagation.

Frequency.

Longitudinal waves.

Porpoise produces ultrasonic waves.

Megaphone works on the principle of multiple reflection of sound. A Megaphone works by forcing the sound that comes from a person's voice into one direction making it louder.

Ultrasonic sound waves.

An echo is a sound that is repeated because the sound waves are reflected back. Sound waves can bounce off smooth, hard objects in the same way as a rubber ball bounces off the ground. Although the direction of the sound changes, the echo sounds the same as the original sound.

1. Loudness.
2. Pitch.
3. Timbre or Quality.

Quality or timbre.

An echo is heard sooner in water because the speed of sound in water is higher than the speed of sound in air.

The conclusion from the observation is that the prongs of tuning fork are vibrating, and the vibrating prongs carry energy which gets transmitted to surrounding medium.

Ear drum starts vibrating when outside sound falls on it.

Longitudinal (sound) waves.

Megaphone.

Sound is a longitudinal wave.

The loudness or softness of a sound is determined basically by its amplitude, so for a loud sound it must have higher amplitude.

Soundboard works on the principle of reflection of sound.

Infrasonic sound waves.

Speed of sound is more in steel (solid medium) as compared to water (liquid medium).

Ceiling and walls are made curved so that sound after reflection reaches the all audience euqally in all direction.

Light travels much faster than sound. Due to this, the flash of lightning is seen first and the sound of thunder is heard a little later.

The sensation of a frequency is commonly referred to as the pitch of a sound. A high pitch sound corresponds to a high frequency sound wave and a low pitch sound corresponds to a low frequency sound wave.

A stethoscope, based on the principle of reflection of sound, is used by doctors to listen to our heartbeats.

Sound travels fastest in solids.

Ears enable us to hear sounds.

Echo is repetition of sound caused by the reflection of sound waves.

It is more convenient to put the ear to the track to hear a train approaching from far away because sound travels faster in solids than in air.

Radio waves are used to communicate with one another on moon.

One way is with a depth gauge. The gauge basically measure differential pressure between pressure inside the boat (kept at atmospheric pressure) and sea pressure outside). Knowing how fast pressure rises as depth increases allows the gauge indication to be calibrated to read out in feet of depth.

The cracks occur due to shock waves produced in the explosion of the bomb.

Longitudinal wave.

The reflection of sound leads to formation of echoes.

Supersonic Speed.

No, we cannot hear infrasonic waves and ultrasonic waves. That’s because the frequencies of both these waves fall beyond the human audible range of frequencies.

The sound waves in air are longitudinal waves.

Infrasonic sound.

The nature of the ocean waves in the deep water is both transverse and longitudinal.

Sound travels faster in iron (being a solid medium).

Sound travels fastest in steel (solid medium).

No, transverse waves cannot travel in glasses.

Transverse, because the vibration of particles of the spring are at right angles to the direction of wave propagation.

Yes, sound can travel through iron and as well as water.

Transverse, because the light waves are electromagnetic waves in which electric and magnetic fields oscillate in the direction at right angles to each other and also to the direction of propagation of the wave.

Supersonic speed refers to the speed of an object which is greater than the speed of sound.

The three tiny bones present in the middle part of ear are: anvil, hammer and stirrup.

Longitudinal, because the direction of vibration of air molecules is to and fro about its mean position along the direction of propagation of wave due to the vibration of quartz crystal.

As the frequency increases the pitch of the sound also increases.

When the school bell vibrates, it forces the adjacent particles in air to vibrate. This disturbance gives rise to a wave and when the bell moves forward, it pushes the air in front of it. This creates a region of high pressures known as compression. When the bell moves backwards, it creates a region of low pressure know as rarefaction. As the bell continues to move forward and backward, it produces a series of compressions and rarefactions. This makes the sound of a bell propagate through air.

• Slowest - Sound
• Fastest - light

Ultrasound scans are used to monitor the growth of developing baby in the uterus of the mother.

The persistence or sound in a big hall or auditorium is called reverberation.

An object should vibrate in order to produce sound.

Stirrup.

Soundboard is a concave board which is kept behind the speaker on the stage of a big hall.

1. Megaphone and bulb horn.
2. Stethoscope.
3. Soundboard.

• Solid - table.
• Liquid - water.
• Gas - air.

Ear canal.

Combination of transverse and longitudinal.

Transverse and Longitudinal waves.

Tuning fork is used to produce sound in laboratory experiments.

Sound waves in air: Longitudinal, Compression, Rarefaction.
Water waves: Transverse, Crest, Trough.

Supersonic is used to denote a speed greater than the speed of sound.

Eustachian tube.

Sound is produced by vibration. When a body vibrates, it forces the neighbouring particles of the medium to vibrate. This creates a disturbance in the medium, which travels in the form of waves. This disturbance, when reaches the ear, produces sound.

Loudness of the sound is measured in decible and ac loudness depends on amplitude it also depends on amplitude of the sound.

Sound travels slowest in gases.

Ultrasonic sounds.

Wavelength, frequency and speed of the sound waves remain the same.

The function of three tiny bones in the ear is to increase the strength of vibrations coming from the ear drum before passing them onto the inner ear.

Vocal cords vibrate in our voice box when we talk.

1. Loudness.
2. Pitch.
3. Timbre.

No, sound cannot travel through vacuum.

Bat navigates and finds its food by echolocation.

It is common observation that in the rainy season, the flash of lightning is seen first and the sound of thunder is heard a little later. That’s because, speed of light is very high as compared to speed of sound in air.

Pitch helps us to distinguish between a man’s voice and a woman’s voice, even without seeing them.

Curtains and carpets can make our big room less echoey.

Transverse waves.

SI unit of frequency is hertz.

Transverse wave.

Auditory nerve.

A megaphone is used to address a small gathering of people.

Drums consist of at least one membrane, called a drumhead or drum skin, that is stretched over a shell and struck, either directly with the player's hands, or with a percussion mallet, to produce sound.

Longitudinal, because the molecules of the liquid vibrate to and fro about their mean positions along the direction propagation of the wave.

Sound Navigation And Ranging.

Longitudinal waves.

The loudness decreases with the decrease in the amplitude of sound.

Sound waves needs material medium to propagate therefore, they are called mechanical waves. Sound waves propagate through a medium because of the interaction of the particles present in that medium.

Hammer.

Transverse waves.

Light travels much faster than sound. Due to this, the flash of gunshot is seen first and the sound of gunshot is heard a little later.

Transverse (water) waves.

Pitch of a sound is directly proportional to frequency. Higher the frequency, higher is the pitch of the sound.

Transverse waves.