Sound and Waves

1

Which one of the following frequency range is sensitive to human ears?

  1. 0 - 200 Hz
  2. 20 - 20000 Hz
  3. 200 - 20000 Hz
  4. 2,000 - 20000 Hz
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2

Which of the following statements about electromagnetic waves, sound waves and water waves is/are correct?

  1. The exhibit reflection.
  2. They carry energy.
  3. They exert pressure.
  4. They can travel in vacuum.

Select the correct answer using the codes given below

  1. 1, 2 and 3
  2. 2 and 4
  3. 1 and 3
  4. Only 1
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3

A person rings a metallic bell near a strong concrete wall. He hears the echo after 0.3 s. If the sound moves with a speed of 340 m/s, how far is the wall from him?

  1. 102 m
  2. 11 m
  3. 51 m
  4. 30 m
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4

A sound wave has frequency of 2 kHz and wavelength of 35 cm. If an observer is 1.4 km away from the source, after what time interval could the observer hear the sound?

  1. 0.5 s
  2. 2 s
  3. 4 s
  4. 20 s
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5

Ultrasonic waves of frequency 3 × 105 Hz are passed through a medium where speed of sound is 10 times that in air (Speed of sound in air is 300 m/s). The wavelength of this wave in that medium will be of the order of

  1. 0.1 cm
  2. 1 cm
  3. 10 cm
  4. 100 cm
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6

Bats can fly in dark because they

  1. have strong wings
  2. have sharp eyes
  3. produce ultrasonic waves
  4. are nocturnal
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7

The speed of a body that has Mach number more than 1 is

  1. supersonic
  2. subsonic
  3. 300 m/s
  4. about 10 m/s
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8

Which one of the following waves does not belong to the category of the other three?

  1. X-rays
  2. Microwaves
  3. Radio waves
  4. Sound waves
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9

Bats detect obstacles in their path by receiving the reflected

  1. Infrasonic waves
  2. Ultrasonic waves
  3. Radio waves
  4. Microwaves
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10

Which one among the following waves carries the maximum energy per photon?

  1. X-rays
  2. Radio waves
  3. Light waves
  4. Microwaves
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11

Which one of the following waves is used for detecting forgery in currency notes?

  1. Ultraviolet waves
  2. Infrared waves
  3. Radio waves
  4. Microwaves
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12

Sound waves cannot travel through a

  1. copper wire placed in air
  2. silver slab placed in air
  3. glass prism placed in water
  4. wooden hollow pipe placed in vacuum
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13

Sound travels in air if

  1. particles of medium travel from one place to another
  2. there is no moisture in the atmosphere
  3. disturbance moves
  4. both particles as well as disturbance travel from one place to another
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14

Ultrasound has frequency of vibration

  1. between 20 and 20,000 Hz
  2. below 20 Hz
  3. above 20,000 Hz
  4. between 500 and 10,000 Hz
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15

Pitch of sound is determined by its

  1. frequency
  2. amplitude
  3. speed
  4. loudness
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16

Loudness of sound is measured in units of

  1. decibel (dB)
  2. hertz (Hz)
  3. metre (m)
  4. metre/second (m/s)
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17

An object is vibrating at 50 hertz. What is its time period?

  1. 0.02 s
  2. 2 s
  3. 0.2 s
  4. 20.0 s
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18

The loudness of sound depends on:

  1. its amplitude
  2. its time period
  3. its frequency
  4. its speed
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