Sound Archives

41. The pitch of a sound wave depends upon which one of its following char

The pitch of a sound wave depends upon which one of its following characteristics ?

Speed

Loudness

Amplitude

Frequency

This question was previously asked in

UPSC CDS-2 – 2022

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The pitch of a sound wave is determined by its frequency. Higher frequency corresponds to a higher pitch, and lower frequency corresponds to a lower pitch.

– Pitch is the quality of a sound governed by the rate of vibrations producing it; the degree of highness or lowness of a tone.
– Frequency is the number of vibrations per unit of time.

Loudness of a sound is related to its amplitude, not frequency. Speed is the rate at which the sound wave travels through a medium and is dependent on the medium’s properties.

42. School bells are made of metals because metals are

School bells are made of metals because metals are

Malleable

Sonorous

Ductile

Lustrous

This question was previously asked in

UPSC CDS-2 – 2022

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School bells, and bells in general, are made of metals because metals possess the property of sonority. Sonority is the ability of a material to produce a clear, deep, resonant ringing sound when struck. This property is characteristic of many metals and alloys, especially when shaped appropriately into a bell. Malleability, ductility, and lustrousness are other properties of metals but are not the reason they are used for making bells that produce sound.

Metals are used for making bells because they are sonorous.

Bronze, a metal alloy (primarily copper and tin), is a historically common material for making high-quality bells due to its excellent sonorous properties.

43. A sound wave has a frequency of 4 kHz and wavelength 30 cm. How long w

A sound wave has a frequency of 4 kHz and wavelength 30 cm. How long will it take to travel 2.4 km ?

2.0 s

0.6 s

1.0 s

8.0 s

This question was previously asked in

UPSC CDS-2 – 2021

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To find the time taken, we first need to calculate the speed of the sound wave using the formula speed (v) = frequency (f) × wavelength (λ). Given f = 4 kHz = 4000 Hz and λ = 30 cm = 0.3 m, the speed is v = 4000 Hz × 0.3 m = 1200 m/s. The distance to travel is 2.4 km = 2400 m. Time (t) = distance (d) / speed (v) = 2400 m / 1200 m/s = 2 seconds.

The speed of a wave is the product of its frequency and wavelength (v = fλ). Time taken to travel a distance is distance divided by speed (t = d/v). Ensure units are consistent (e.g., meters and seconds).

Frequency is the number of waves passing a point per second (Hz), and wavelength is the distance between successive crests or troughs (m). Kilohertz (kHz) is 1000 Hz, and a kilometer (km) is 1000 meters. Centimeter (cm) is 0.01 meters. Proper unit conversion is crucial for calculations.

44. Which one of the following phenomena verifies the fact that light trav

Which one of the following phenomena verifies the fact that light travels much faster than sound?

Twinkling of stars in night sky

Lighting of a matchstick

Thunderstorm

Mirage

This question was previously asked in

UPSC CDS-2 – 2020

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The phenomenon of a thunderstorm clearly demonstrates that light travels much faster than sound. During a thunderstorm, lightning is a visual flash of light, and thunder is the sound produced by the rapid expansion of air heated by the lightning discharge. We always see the lightning first and then hear the thunder after a noticeable delay. This delay is because light travels at approximately 3 x 10⁸ meters per second, while sound travels at approximately 343 meters per second in air (at 20°C), a speed difference of about a million times.

The time difference between seeing lightning and hearing thunder during a thunderstorm proves that light travels significantly faster than sound.

Twinkling of stars is due to atmospheric refraction and unrelated to the speed of sound. Lighting a matchstick involves processes happening over very small distances where the speed difference isn’t noticeable. A mirage is an optical phenomenon related to atmospheric refraction and temperature gradients, not the speed difference between light and sound.

45. The frequency (in Hz) of a note that is one octave higher than 500 Hz

The frequency (in Hz) of a note that is one octave higher than 500 Hz is

375

750

1000

2000

This question was previously asked in

UPSC CDS-2 – 2019

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The frequency of a note that is one octave higher than 500 Hz is 1000 Hz.

– In music and acoustics, an octave is an interval between two notes where the higher note has a frequency exactly double that of the lower note.
– Conversely, a note one octave lower than a given note has half its frequency.

This relationship between frequency and octave is fundamental to musical scales and harmony. For example, if A4 is tuned to 440 Hz, A5 (one octave higher) is 880 Hz, and A3 (one octave lower) is 220 Hz.

46. An echo is heard after 5 seconds of the production of sound which move

An echo is heard after 5 seconds of the production of sound which moves with a speed of 340 m/s. What is the distance of the mountain from the source of sound which produced the echo ?

0.085 km

0.85 km

0.17 km

1.7 km

This question was previously asked in

UPSC CDS-2 – 2019

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An echo is produced when sound reflects off a surface and returns to the source. The sound travels from the source to the mountain and then back from the mountain to the source. The total distance covered by the sound in 5 seconds is given by distance = speed × time = 340 m/s × 5 s = 1700 meters. This total distance is twice the distance between the source and the mountain (since the sound goes there and back). Therefore, the distance of the mountain from the source is half of the total distance, which is 1700 m / 2 = 850 meters.

In an echo scenario, the time measured is for the sound’s round trip (source to obstacle and back), so the distance to the obstacle is half the total distance traveled by the sound.

To convert meters to kilometers, divide by 1000. So, 850 meters = 850 / 1000 km = 0.85 km. This matches option B.

47. Ultrasonic waves are produced by making use of

Ultrasonic waves are produced by making use of

ferromagnetic material

ferrimagnetic material

piezoelectric material

pyroelectric material

This question was previously asked in

UPSC CDS-2 – 2017

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Ultrasonic waves are commonly produced by utilizing the piezoelectric effect, typically in materials like quartz crystals or certain ceramics.

Piezoelectric materials convert electrical energy into mechanical vibrations and vice versa. By applying a high-frequency alternating voltage across a piezoelectric crystal, it vibrates at that frequency, generating ultrasonic waves.

The piezoelectric effect is reversible. Piezoelectric materials are used in ultrasonic transducers for various applications, including medical imaging (ultrasound scans), sonar, industrial testing (non-destructive testing), and cleaning (ultrasonic cleaners).

48. Consider the following statements about the microphone and the speaker

Consider the following statements about the microphone and the speaker of a mobile phone :

1. The microphone converts sound to a mechanical signal.
2. The microphone converts sound to an electrical signal.
3. The speaker converts a mechanical signal to sound.
4. The speaker converts an electrical signal to sound.

Which of the statements given above are correct?

1 and 3

1 and 4

2 and 3

2 and 4

This question was previously asked in

UPSC CDS-1 – 2023

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A microphone is a transducer that converts sound waves (acoustic energy) into electrical signals. This electrical signal is then processed. A speaker is also a transducer that converts an electrical signal back into sound waves (acoustic energy). Therefore, statement 2 (microphone converts sound to an electrical signal) and statement 4 (speaker converts an electrical signal to sound) are correct. Statements 1 and 3 involving “mechanical signal” in this context are incorrect as the primary conversion involves energy forms like sound and electricity, mediated by mechanical *vibrations* but the output/input are electrical/sound signals.

Microphones convert sound energy into electrical energy. Speakers convert electrical energy into sound energy.

Microphones typically work by diaphragm vibration caused by sound waves, which then generates an electrical signal (e.g., carbon, dynamic, condenser microphones). Speakers work by an electrical current flowing through a coil in a magnetic field, causing the coil (and an attached diaphragm/cone) to vibrate, producing sound waves.

49. A person burned a firecracker in front of a cliff and heard its echo 5

A person burned a firecracker in front of a cliff and heard its echo 5 s after it burst. The distance of the cliff from the person, if the speed of the sound is 340 m/s, is close to

1700 m

170 m

85 m

850 m

This question was previously asked in

UPSC CDS-1 – 2023

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The time taken for the echo to be heard is the time it takes for the sound to travel from the person to the cliff and then back to the person. The total distance covered by the sound is therefore twice the distance between the person and the cliff. Given the speed of sound (v) is 340 m/s and the total time (t) for the echo is 5 s, the total distance (d_total) is v × t = 340 m/s × 5 s = 1700 m. The distance to the cliff (d_cliff) is half of the total distance: d_cliff = d_total / 2 = 1700 m / 2 = 850 m.

The total distance covered by an echo is twice the distance to the reflecting surface. Distance = Speed × Time.

Echo is the reflection of sound waves from a surface. The time delay between the original sound and the echo is used to determine the distance of the reflecting surface. This principle is used in sonar and ultrasound imaging.

50. The property of the sound waves that determines the pitch of the sound

The property of the sound waves that determines the pitch of the sound is its

frequency

amplitude

wavelength

intensity

This question was previously asked in

UPSC CDS-1 – 2020

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The pitch of a sound is the quality that allows us to judge whether a sound is high (like a whistle) or low (like a drum). This quality is directly determined by the frequency of the sound wave. A higher frequency corresponds to a higher pitch, and a lower frequency corresponds to a lower pitch.

– Pitch is the subjective perception of the frequency of sound.
– Higher frequency means higher pitch.
– Amplitude relates to loudness or intensity.

While frequency is the primary determinant of pitch, other factors like the intensity of the sound can also slightly influence the perceived pitch, especially at very high or very low frequencies. However, for practical purposes, frequency is considered the defining characteristic for pitch.