Sonometer Practical Viva Questions and Answers
(i) Does sound travel in vaccum?
Ans: No, A material medium is needed for its propagation
(ii) What are the frequency limits of audibility?
Ans: 20 Hz and 20,000 Hz
(iii) What type of waves are light waves and sound waves?
Ans: (a) Transverse (b) Longitudinal
(iv) On what factors does the frequency of a tuning fork depend?
Ans: It depends on the nature of the material and length of the prong
(v) What type of waves are produced in a sonometer wire?
Ans: In the tuned position stationary waves are produced. Otherwise there are transverse waves
(vi) Why is the wooden box of the sonometer hollow?
Ans: Air in the box vibrates in resonance and increases the intensity of sound.
(vii) What are the functions of the bridges?
Ans: They reflect the sound and produce stationary waves
(viii) Can a rubber cord be used in place of the wire?
Ans: The rubber cord is not rigid and so its vibration die down quickly.
(ix) What are beats?
Ans: When two notes of nearly equal frequencies are sounded together there is waxing and waning of sound ie, ups and downs in intensity. This phenomenon is called beats.
(x) What happen when the paper rider in the sonometer experiment flies off'?
Ans: It happens when the frequency of the wire between the bridges and the tuning fork are exactly equal.
(xi) What happen to the frequency of the turning fork when one of the prongs is loaded with wax?
Ans: The frequency of the fork decreases
(xii) What are the factors on which frequency of the segment of a string depends?
Ans: n ∝ 1/l ; n ∝ 1/√T and n ∝ 1/√m
(xiii). What is a sonometer?
Sonometer is an instrument used to measure the frequency of a vibrating body producing sound.
(xiv). What type of waves are produced in a sonometer wire?
In a sonometer wire stationary waves are produced which are transverse in nature.
(xv). What is the function of knife edges placed below the wire of the sonometer?
The transverse waves produced in the wire get reflected from the knife edges resulting in stationary waves.
(xvi). What is the function of 'rider' in sonometer experiment?
The rider will fly off only when the vibrations produced in the wire of very large amplitude. This happens only when the frequency of vibration of the wire becomes equal to that of tuning fork at resonance.
(xvii). What is meant by transverse wave?
If the particles of the medium vibrate perpendicular to the propagation of the wave motion, it is called transverse wave.
(xviii). What is meant by progressive wave?
A wave that propagates in an extended medium without attenuation is called progressive wave.
(xix). What is meant by stationary wave?
When two waves of same type propagate along a straight line, but in opposite directions, their superposition upon each other gives a resultant wave which does not travel either way with time is called stationary wave.
(xx). Define wavelength.
Wavelength of a wave is the distance travelled by the wave during a periodic time.
(xxi). Why is the wooden box of sonometer hollow?
A hollow wooden box may enclose air which vibrates in resonance and increases the intensity of sound.
(xxii). Define node.
In a stationary wave, point where zero amplitude is called node.
(xxiii). Define antinode.
In a stationary wave, the points where maximum amplitude is called antinodes.
(xxiv). What is the distance between two consecutive nodes or antinodes?
λ/2 (half the wavelength λ)
(xxv). Define beats.
The phenomenon of regular variation in the intensity of sound with time at a particular position, when two sound waves of nearly equal frequencies, superimpose on each other is called beats.
(xxvi). What is a fundamental note?
It is a note of the lowest frequency.
(xxvii). What are overtones?
Overtones are notes whose frequencies are simple multiples of the fundamental notes.
(xxviii). What is meant by unison?
Two notes of same frequency are said to be in unison.
(xxix). Define pitch.
Pitch is a characteristic of musical sound, which distinguishes a sharp sound from a dull sound.
(xxx). How does the loading or filling at the prongs of a tuning fork affect its frequency?
The frequency of the tuning fork decreases by loading and increases by filling at the prongs.
(xxxi) Aim of Sonometer experiment?
To find the relation between frequency and length, for a constant tension, frequency and diameter of a stretched string.
(xxxii) Apparatus for the Sonometer experiment?
Sonometer, slotted weights, tuning forks of known frequencies, rubber hammer, paper rider, steel wire, etc. The sonometer consists of a long hollow wooden box with a peg at one end and a vertical pulley at the other end. One end of the experimental wire is attached to the peg and the other passes over the pulley. To keep the wire under tension, a suitable weight is suspended at the free end of the string by a weight hanger. Two movable bridges A and B are provided for the purpose of altering the vibrating length of the wire.
(xxxiii) Theory of Sonometer experiment?
The frequency n of transverse vibration of a string stretched under a constant tension T is inversely proportional to the length l of the string.
i.e., n ∝ (1/l);
Therefore, n x l = a constant
(xxxiv) Procedure of Sonometer experiment?
The bridges A and B are placed at a small distance apart. A light paper rider is placed on the string between the bridges. A tuning fork of frequency n is excited and its stem is pressed on the sonometer box between the bridges. The length of the string is altered by adjusting the distance between the bridges till the rider vibrates vigorously. This happens when the segment AB of the string vibrates in unison with the tuning fork. The length l of the vibrating segment is measured and n x l is calculated.
The experiment is repeated with the other tuning forks without changing the tension. In all cases it is found that nl is a constant.
A graph is plotted with n along the X-axis and (1/l) along the Y-axis. The graph is found to be straight line. This also shows that n ∝ (1/l).