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).