Mix Example - SOUND Questions in English

(C) Sound is a mechanical wave that requires a material medium (like air, water, or solids) to propagate.
Space between the Moon and the Earth is a vacuum, meaning there is no medium for the sound waves to travel through.
Since sound cannot travel through a vacuum, the sound of the explosion on the Moon will never reach the Earth.
Therefore, the correct answer is that it will not reach the Earth, which corresponds to the option 'None of these'.

(D) The walls,ceiling,and floor of a hall built for musical concerts are designed to absorb sound to prevent excessive reverberation or echoes. If the sound is reflected too much,it creates a confusing overlap of sounds,making the music unclear. Therefore,materials like sound-absorbing boards,heavy curtains,or acoustic panels are used to ensure high sound quality.

(A) The quality or timbre of a sound is the characteristic that allows us to distinguish between sounds of the same pitch and loudness produced by different sources.
Even if two instruments play a note of the same pitch and loudness,the waveform of the sound produced by each instrument is unique due to the presence of different overtones or harmonics.
Therefore,the human ear can identify the source of the sound based on its quality or timbre.

(B) The loudness of a sound is directly proportional to the amplitude of the vibration. $A$ larger bell has a larger surface area,which allows it to vibrate with a greater amplitude when struck. Consequently,a larger bell produces a sound with greater intensity or loudness,which can travel over a longer distance. Therefore,temple bells are made large to produce a loud sound.

(C) Sound is a mechanical wave that requires a material medium (like air,water,or solids) to travel from one point to another.
On the surface of the Moon,there is no atmosphere,which means it is a vacuum.
Since there is no medium for the sound waves to propagate,an astronaut cannot hear their companion's voice directly through the air.

(D) The loudness of a sound is a measure of the sound's intensity,which is directly related to the energy carried by the sound wave.
Loudness is determined by the amplitude of the vibration.
Greater amplitude results in a louder sound,while smaller amplitude results in a quieter sound.
Therefore,the correct option is $D$.

(A) Sound is a mechanical wave that requires a material medium for its propagation.
In the bell jar experiment,as the air is pumped out,the density of the medium (air) inside the jar decreases.
Since sound intensity depends on the density of the medium and the amplitude of the vibrations,the reduction in air molecules leads to a decrease in the energy transmitted.
Consequently,the intensity of the sound heard by the observer gradually falls until it becomes inaudible when a vacuum is created.

(B) The statement is $False$. Sound waves are $longitudinal$ waves because the particles of the medium vibrate parallel to the direction of wave propagation. In contrast,light waves are $electromagnetic$ waves,which are $transverse$ in nature,meaning the oscillations occur perpendicular to the direction of wave travel.

(FALSE) The statement is False.
In a wave motion,the distance between two consecutive crests or two consecutive troughs is equal to the wavelength,denoted by $\lambda$.
The distance from a crest to the immediately following trough represents half of a wavelength,which is $\lambda / 2$.

(A) The statement is True. The human ear can detect sound waves with frequencies ranging from $20 \, Hz$ to $20,000 \, Hz$ (or $20 \, kHz$). This range is known as the audible range.

(TRUE) The relationship between frequency $(f)$ and time period $(T)$ is given by the formula: $f = 1/T$.
Given that the time period $T = 0.01 \, s$.
Substituting the value into the formula: $f = 1 / 0.01 = 100 \, Hz$.
Therefore,the statement is True.

(B) The statement is False.
For an echo to be heard distinctly,the time interval between the original sound and the reflected sound must be at least $0.1\, s$.
Given the speed of sound in air is approximately $344\, m/s$,the total distance traveled by the sound (to the reflector and back) is given by: $\text{Distance} = \text{Speed} \times \text{Time} = 344\, m/s \times 0.1\, s = 34.4\, m$.
Since the sound travels to the reflector and back,the minimum distance between the source and the reflector is half of the total distance: $34.4\, m / 2 = 17.2\, m$.
Therefore,the minimum distance required is $17.2\, m$,not $34\, m$.

(FALSE) The statement is False.
Sound waves are mechanical waves that require a medium to travel.
The speed of sound depends on the density and elasticity of the medium.
Generally,sound travels faster in solids,followed by liquids,and slowest in gases.
Since water is a liquid and air is a gas,sound travels significantly faster in water (approximately $1480 \ m/s$) compared to air (approximately $343 \ m/s$ at $20^{\circ}C$).

(TRUE) The statement is True.
Sound waves require a medium to travel. The speed of sound in a gas depends on the temperature of the medium. As the temperature increases,the kinetic energy of the gas molecules increases,causing them to vibrate more rapidly and collide more frequently. This increased molecular activity allows the sound wave to propagate through the medium more quickly. Therefore,the speed of sound is directly proportional to the square root of the absolute temperature of the gas.

(FALSE) The statement is False.
Sound waves are longitudinal waves that travel in a medium in the form of compressions and rarefactions.
Light waves are electromagnetic waves (transverse waves) that travel in a medium in the form of crests and troughs.

(B) The statement is False.
Given: Frequency $(f)$ = $5\, MHz = 5 \times 10^6\, Hz$,Velocity $(v)$ = $1540\, m s^{-1}$.
The formula for wavelength $(\lambda)$ is $\lambda = \frac{v}{f}$.
Substituting the values: $\lambda = \frac{1540}{5 \times 10^6} = 308 \times 10^{-6}\, m = 0.308 \times 10^{-3}\, m = 0.308\, mm$.
Since $0.308\, mm \neq 0.3\, mm$,the statement is False.

(A) The statement is True.
Light waves are electromagnetic waves,which consist of oscillating electric and magnetic fields.
Unlike mechanical waves (such as sound waves),electromagnetic waves do not require a material medium to travel.
Therefore,light can propagate through a vacuum,such as outer space.

(A) The frequency of the sounding body is $f = 300 \text{ Hz}$.
Time taken to produce $30$ vibrations is calculated as $t = \text{number of vibrations} / \text{frequency} = 30 / 300 = 0.1 \text{ s}$.
Assuming the speed of sound in air is $v = 340 \text{ m/s}$,the distance covered by the sound in $0.1 \text{ s}$ is $d = v \times t = 340 \text{ m/s} \times 0.1 \text{ s} = 34 \text{ m}$.
Since the calculated distance matches the statement,the statement is True.

(FALSE) The statement is False. In a non-dispersive medium like air,the speed of sound is independent of frequency. The speed of sound depends primarily on the properties of the medium,such as temperature,pressure,and density,not on the frequency or wavelength of the sound wave.