Answer:
1. Answer : (c) rhinoceros
Explanations: Rhinos have extremely good ears, picking up "infrasound" far deeper than the range of human hearing.
2. Answer : (a) ultrasonic waves
Explanations: Ultrasonic waves are used in SONAR instead of audible sound waves. SONAR uses ultrasonic waves i.e. sounds having a frequency greater than 20,000 Hz.
3. Answer : (b) amplitude
Explanations: Loudness is directly proportional to the amplitude of a sound. The larger the amplitude the louder the sound and the more energy the sound waves contain. Hence, when we change feeble sound to loud sound we increase its amplitude. Hence option B is the correct answer.
4. Answer : (b) infrasound
Explanations: Earthquake is basically the sudden movement of tectonic plates of the earth which causes tremor of earth crust and it produces infrasound before the main shock wave begins during this process there is a sudden release of seismic waves that makes the ground shake and these seismic waves are classed as infrasound waves.
5. Answer : (a) Amplitude
Explanations: The amplitude of a rope wave depends on how hard you shake it. For a sound wave, it depends on how much compression the loudspeaker or musical instrument creates. In other words, it depends on the energy the source put into the wave. It does not depend on frequency, wavelength, or velocity.
6. Answer : (c) 25 kHz
Explanations: The children under age 5 years have fully developed inner and middle ears allowing them to hear from 20 Hz to 25,000 Hz. As age increases, our inner ear changes gradually which causes a reduction in hearing capacity from 20 Hz to 20,000 Hz.
7. Answer : (b) vibrating
Explanations: Sound is produced by the vibration of an object. When an object vibrates back and forth in the air, then the molecules of air close to this object also start vibrating back and forth with the same frequency.
8. Answer : (c) At the right angles to the direction of wave propagation
Explanations: In a transverse wave when the wave moves forward, the particles of the medium vibrate perpendicular to the direction of motion of the wave.
9. Answer : (a) 20 kHz
Explanations: Humans can detect sounds in a frequency range from about 20 Hz to 20 kHz. (Human infants can actually hear frequencies slightly higher than 20 kHz, but lose some high-frequency sensitivity as they mature; the upper limit in average adults is often closer to 15–17 kHz.)
10. Answer : (a) supersonic speed and pressure variation.
Explanations: A sonic boom is a sound associated with shock waves created when an object travels through the air faster than the speed of sound. As the object moves, this conical region also moves behind it and when the cone passes over the observer, they will briefly experience the boom. Sonic booms are caused by the combination of. supersonic speed and pressure variation.
11. Answer : (d) oscillatory
Explanations: In a transverse wave, the motion of the particles of the medium is at right angles (i.e., transverse) to the direction the wave moves. In a longitudinal wave, such as a sound wave, the particles oscillate along the direction of motion of the wave.
12. Answer : (b) Wave motion
Explanations: Wave motion is the propagation of a disturbance produced in a medium by the repeated periodic motion of the particles of the medium. In all progressive waves, energy travels through the medium in the direction in which the wave travels.
13. Answer : (c) amplitude
Explanations: The amplitude of the wave is the maximum displacement of the particle from its mean position. It is the property, which determines the loudness of the sound. The amplitude and the loudness are directly proportional, i.e., the greater the amplitude the sound is characterized by a greater loudness.
14.Answer : (d) space
Explanations: Sound vibration must travel through matter. Sound cannot travel through a vacuum. A vacuum is an area without any air, like space. So sound cannot travel through space because there is no matter for the vibrations to work in.
15.Answer : (a) hertz
Explanations: The SI unit for frequency is the hertz (Hz). One hertz is the same as one cycle per second.
16.Answer : (a) Increases
Explanations: As the temperature increases the molecules in the air acquire more energy and the molecules vibrate faster. Since the molecules vibrate faster, the sound wave travels through the air faster because the sound wave is propelled by the collision of molecules in the air.
17.Answer : (a) Ultrasound
Explanations: Bats are able to fly at night without colliding with other objects because they emit ultrasonic squeaks and listen to the echoes produced by the reflection of their squeaks from the objects or obstacles in their path.
18. Answer : (b) Slinky
Explanations: Slinky can produce longitudinal as well as transverse waves.
19. Answer : (b) 0.2 m
Explanations: velocity = frequency \(\times\) wavelength
⇒ 380 = 1900 \(\times\) wavelength
⇒ wavelength \(=\frac{380}{1900}\)
⇒ wavelength = \(\frac{38}{190}\)
⇒ wavelength = 0.2
20. Answer : (a) Rarefaction
Explanations: Rarefactions are areas of ultrasound wave having low pressure as the distance of their particles is far while compressions are areas having high pressure as the distance of their particles is close.
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