Class 8 Science Chapter 10 MCQ

Since, loudness depends upon amplitude, so it can be increased by increasing amplitude and it can be decreased by decreasing amplitude.

Unit of loudness of sound is decibel (dB).

Loudness of sound is determined by the amplitude of its vibration.

Here, all the statements are correct. Hence, your answer will be option [D].

Pitch or shrillness is determined by the frequency of sound.

Here, all the statements are correct. Hence, your answer will be option [D].

Ultrasound has frequency of vibration above 20,000 Hz.

Because light can travel in vacuum also but it is only sound which requires medium to travel.

We know that = Frequency = 1 / Time period Time period = 1 / Frequency = 1 / 50 = 0.02 s

Oscillation = 10, Time taken = 20 s As we know that the number of oscillations per second is frequency. Frequency = No. of oscillations / Time taken = 10 / 20 = 0.5 Hz. Time period = 1 / Frequency = 1 / 0.5 = 2 s

We know that, Distance = Speed x Time = 330 x 5 = 1650 m = 1.65 km (1 km = 1000 m, speed of sound = 330 m/s) So, she is standing at 1.65 km from the place where lighting occurs.

The three tiny bones in the middle part of ear act as a system of levers and sound vibration passing them on the “cochlea” not in brain. Cochlea sets up the vibrations or electrical impulses by auditory nerve to the brain.

Metal plates vibrates when a musical note is produced by the cymbals in an orchestra. Cymbals is a musical instrument which produces sound when being struck. The person who plays cymbals is called cymbalist. It has two discs which is made up of various alloys. It is used in metal and heavy bands, orchestra, percussion ensembles and marching groups.

Hearing Aid is a small sound amplifying device worn on the ear by a partially deaf person not deaf person.

Humans are capable of hearing sound waves of frequency between 20 Hz and 20,000 Hz only. This is called the Sonic waves. These audio frequencies are called the audible range. The sound above this range is called ultra-sonic and below it is called sub sonic. Humans are not capable of hearing both the sub sonic and ultra-sonic frequencies. Thus, option [C] 15 kHz and 25 Hz is correct answer because the human audible range is 20Hz to 20,000 Hz.

A violin and a flute may both be played at the same time in an orchestra. Both sounds travel through the same medium, that is, air and arrive at our ear at the same time. Both sounds travel at the same speed irrespective of the source. But the sounds we receive are different. This is due to the different characteristics associated with the sound. Generally, tone and note should be matched in pleasant way. So, the sitarist adjusts the frequency of sitar according to other musical instruments. Only if all the musical instruments are in the same frequency, will the output will be in unison. Otherwise, the music will not be pleasing to the hear’s ears.

When the mechanical piano is struck harder the second time, we find sound will be louder but pitch remains the same because the frequency has not changed. The pitch depends on frequency of the particular key which is being hit and hence there would be no change in pitch of sound. In another words, when the key of a mechanical piano struck harder, the vibrations caused are more resulting in larger amplitude of the wave that propagates from the key. Loudness depends on the square of the amplitude of the wave. Amplitude is the size of the vibration, and this determines how loud the sound is. Larger vibrations make a louder sound. Pitch of the sound depends on the frequency of the wave which is not change when the key is struck harder.

The number of oscillations per second is called the frequency of oscillation. Frequency is expressed in hertz. Its symbol is Hz. A frequency of 1 Hz is one oscillation per second. Speed of highly penetrating ultrasonic waves is greater than 20,000 Hz are known as ultrasonic waves or ultrasound. Speed of the audible and ultra-sonic sound are same but waves lengths are different.

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

Timbre or rhythm or modulation can distinguish between the musical sounds produced by different singers on the basis of the characteristic of sound. Sounds may be generally characterized by pitch, loudness, and quality. Sound quality or timbre describes those characteristics of sound which allow the ear to distinguish sounds which have the same pitch and loudness. Timbre is general term for the distinguishable characteristics of a tone. Hence, the quality or timbre of sound is that characteristic which enables us to distinguish one sound from one person to another having the same pitch and loudness

Here, all the statements are correct. Hence, your answer will be option [D].

Remember, the speed of sound in liquids is more than gas but less than solids. i)Sound travels at a speed of 5000 meters per second through iron or steel. [Suppose this is M] ii)The speed of sound in air is 340 meters per second. [Suppose this is N] iii) Sound cannot travel in vacuum. [Suppose this is O] iv)The speed of sound in water is 1500 meters per second. [Suppose this is P] Hence, your answer will be option [D] that is P.

Here, all the statements are correct. Hence, your answer will be option [D].

Mosquito vibrates 500 vibration in 1 second. As, time period is the time taken to complete one vibration. So, Time period = Time taken / Number of oscillations Time period = 1 / 500 = 0.002 seconds