Question

Match the items of Column A with the corresponding items of Column B.

Column 1	Column 2
Sound waves of frequency less than $20Hz$	$20Hz\text{to}20,000Hz$
Second's pendulum	wavelength
Audible range of frequency	cycle per second
Distance between two successive compressions	about $340m{s}^{-1}$
Unit of frequency	infrasonic waves
Speed of sound waves in air	time period is $2s$

Answer 1

Sound waves of frequency less than $20Hz$ - infrasonic waves

1. Hertz $\left(Hz\right)$ is a unit used to measure the frequency of sound.
2. When a vibrating body completes $60$ vibrations in one minute, the frequency of that body is said to be $1Hz$.
3. Humans cannot hear sound waves of frequency less than $20Hz$, and these waves are called infrasonic waves.

Second's pendulum - time period is $2s$

1. When a pendulum moves from one extreme position to another extreme position and then back to the first extreme position, it is said to be one oscillation.
2. The time taken to complete one oscillation is called its time period.
3. A pendulum with a time period of $2s$ is called a second's pendulum.

Audible range of frequency - $20Hz\text{to}20,000Hz$

1. Sound waves of frequency below $20Hz$ are known as infrasonic frequency and cannot be perceived by the human ear.
2. Sound waves of frequency above $20,000Hz$ are known as ultrasonic frequency. It is beyond the limit of sound that can be heard by humans.
3. Hence, the audible range, or the sound that can be heard by humans should be between $20Hz\text{to}20,000Hz$.

Distance between two successive compressions - wavelength

1. In a longitudinal wave, the distance between two consecutive compression or two consecutive rarefaction is called wavelength.
2. In a transverse wave, the distance between two consecutive crests or two consecutive troughs is called wavelength.
3. It is the distance after which the pattern of wave motion repeats itself.

Unit of frequency - cycle per second

1. The number of oscillations made per second by the vibrating body is called its frequency.
2. It is represented by the equation $f=\frac{1}{T}$, where $f$ is the frequency and $T$ is the time period.
3. The unit of frequency is hertz or cycle per second, because oscillations start and end at the same position, so it can be termed as cycle.

Speed of sound waves in air - about $340m{s}^{-1}$

1. Sound requires a material medium for its propagation.
2. As compared to light, the speed of sound is much less and depends on the material through which it is travelling.
3. Sounds travels faster is solids, comparatively slower in liquids and slowest in gases.
4. The speed of sound in air is about $340m{s}^{-1}$.

The items of Column A with the corresponding items of Column B are matched below:

COLUMN A	COLUMN B
Sound waves of frequency less than $20Hz$	infrasonic waves
Second's pendulum	time period is $2s$
Audible range of frequency	$20Hz\text{to}20,000Hz$
Distance between two successive compressions	wavelength
Unit of frequency	cycle per second
Speed of sound waves in air	about $340m{s}^{-1}$