Which of the following pairs is correctly matched? 1. Infrasound : Frequency 20 kHz 3. Audible Range : 20 Hz – 2000 Hz Select the correct answer using the code given below:

The correct option is 1 and 2 only Explanation Sound waves are longitudinal mechanical waves classified based on their frequency relative to the human hearing capacity. The acoustic spectrum is divided into three main categories: infrasonic, audible, and ultrasonic waves. Statement-wise Analysis: - Statement 1 is Correct: Infrasound refers to sound waves with frequencies below the lower limit of human audibility, which is 20 Hz. These waves are produced by sources such as earthquakes, volcanoes, and certain animals like whales and elephants. - Statement 2 is Correct: Ultrasound refers to sound waves with frequencies exceeding the upper limit of human audibility, which is 20,000 Hz (20 kHz). These waves are utilized in applications such as SONAR and medical ultrasonography. - Statement 3 is Incorrect: The Audible Range for the average human ear extends from 20 Hz to 20,000 Hz (20 kHz). The statement incorrectly cites the upper limit as 2000 Hz. Frequencies above 20 kHz are inaudible to humans. Key Takeaway: The classification of sound by frequency is: Infrasound ( 20 kHz).

Which of the following pairs is correctly matched? 1.… - NCERT Class 9 Science MCQ

NCERT Class 9 Science — Chapter 5: Sound

mcqeasy

Which of the following pairs is correctly matched?

Infrasound : Frequency < 20 Hz
Ultrasound : Frequency > 20 kHz
Audible Range : 20 Hz – 2000 Hz

Select the correct answer using the code given below:

NCERT textbook question

From NCERT Science - class 9 · Page 9

Options

A1, 2 and 3
B2 and 3 only
C1 and 2 only
D1 and 3 only

Did you get this right?

Solution

The correct option is

1 and 2 only

Explanation

Sound waves are longitudinal mechanical waves classified based on their frequency relative to the human hearing capacity. The acoustic spectrum is divided into three main categories: infrasonic, audible, and ultrasonic waves.

Statement-wise Analysis:

Statement 1 is Correct: Infrasound refers to sound waves with frequencies below the lower limit of human audibility, which is 20 Hz. These waves are produced by sources such as earthquakes, volcanoes, and certain animals like whales and elephants.
Statement 2 is Correct: Ultrasound refers to sound waves with frequencies exceeding the upper limit of human audibility, which is 20,000 Hz (20 kHz). These waves are utilized in applications such as SONAR and medical ultrasonography.
Statement 3 is Incorrect: The Audible Range for the average human ear extends from 20 Hz to 20,000 Hz (20 kHz). The statement incorrectly cites the upper limit as 2000 Hz. Frequencies above 20 kHz are inaudible to humans.

Key Takeaway:
The classification of sound by frequency is: Infrasound (< 20 Hz), Audible Sound (20 Hz – 20 kHz), and Ultrasound (> 20 kHz).

Your note

More from Chapter 5: Sound

Consider the following statements about the 'Hearing Aid': 1. It is a battery-operated electronic device. 2. The microphone converts electrical signals into sound. 3. The speaker converts sound waves into electrical signals. Which of the statements given above is/are correct?

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What is the primary purpose of designing curved ceilings in concert halls and cinema halls?

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"A violin and a flute may be played at the same time... but the sounds we receive are different." This difference is primarily due to which characteristic of sound?

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With reference to the audible range of sound, consider the following statements: 1. The audible range for an average human is 200 Hz to 200,000 Hz. 2. Sounds with frequencies below 20 Hz are called infrasound. 3. Rhinoceroses communicate using infrasound. Which of the statements given above are correct?

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Ordinary sound waves are unsuitable for detecting flaws in metal blocks primarily because:

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