Apparatus:
Resonance tube apparatus, pinch cock, vernier callipers, thermometer, two tuning forks of known frequency, rubber pad, set square and beaker.
Observations:
Room temperature at the beginning = t1 oC
Room temperature at the end = t2 oC
Mean Room temperature = t = (t1 + t2) / 2 =…… oC
Position of the open end of the tube against the scale = X =………..cm.
|
No. of obs |
f Hz |
First resonance position level |
L1= A-X |
Second resonance | L2=B-X | l = l2-l1 cm | ||||
| Falling A1 |
Rising A2 |
Mean ‘A’ | Falling |
Rising |
Mean ‘B’ | |||||
| cm | cm | Cm | cm | Cm | cm | |||||
|
1 2 |
||||||||||
|
1 2 |
||||||||||
Calculations:
Velocity of sound at temperature at t ℃ (With 1st tuning fork) = V1t = 2f1 x l =….. cm / sec
Velocity of sound at temperature at t ℃ (With 2nd tuning fork) =V2t = 2f2 x l = …… cm / sec
Mean value of velocity at t °℃ = Vị =(Vit + V2t ) / 2 =…….. cm / sec.
Velocity of sound at 0℃ = Vo = Vt– 6lt = ……… cm / sec.
Actual value of velocity of sound at 0℃ =……. cm / sec.
Percentage error =………….%
Procedure:
Place the apparatus on a smooth horizontal surface. Check the level of apparatus with plumb line and adjust it with foot screws. Note the temperature of water at the start of the experiment with a thermometer. Note the position of upper end of the resonance tube against the scale and assign as ‘X’. Bring the water reservoir to its highest point and then open the pinch-cock. Strike the tuning fork of known frequency say 512 Hz on a rubber pad gently and held it horizontally over the upper end of the tube. Lower the water level by opening the pinch-cock gradually till the tube resounds with a loud note. Select the position of a resonance tube where the tube resounds maximum. Note this position with the help of set squares for the level falling. Similarly for second position of resonance, take the water level down still further, two times more (above three times to the first position) approximately. Now start vibrating the tuning fork along with the water level going down in the tube. A resound will be heard, less than in case of Ist position. Check this positional while water is rising. Take the mean value as B and find air column as [2. Repeat this experiment with the second tuning fork. Note the temperature of water at the end of the experiment, calculate the velocity of sound at 0℃ using the formula as given above in the calculations.
VIVA -VOCE
Q-1 What is meant by resonance?
A- The marked increase in amplitude of a vibrating body under the influence of periodic force,whose time period is equal to the natural time period of the body is called resonance.
Q-2 What types of waves are produced in the air column in the tube?
A- Longitudinal stationary waves are produced in the air column in the tube.
Q-3 What is the effect of pressure on the velocity of sound?
A- There is no effect of pressure on the velocity of sound.
Q-4 What is the effect of temperature on the velocity of sound?
A- The velocity of sound increases with increase in temperature. For 1℃ rise in temperature, the increase in the velocity of sound is 61 cm/sec (i.e. 0.61 m/sec).
Q-5 What is end correction?
A- The anti node in the resonance tube does not be at the open end of the tube but slightly above it.Thus, a correction is applied for this anti-node shift which is known as end correction. Its value is 0.3D, where D is the internal diameter of the resonance tube.
Q-6 What is the role of water in resonance tube?
A- It simply changes the length of air column in the resonance tube.
Q-7 What is wave motion?
A- It is a form of disturbance which travels through a medium and is due to the periodic motion of the particles of the medium about their mean position.
Q-8 Distinguish between transverse waves and longitudinal waves?
A- Transverse waves consists of crest and trough and the particles of the medium vibrate perpendicular to the direction of wave of propagation. Longitudinal waves consists of compression and rare faction and the particles of the medium vibrate parallel to the direction of wave of propagation.
Q-9 What is the effect of presence of water vapours on the velocity of sound?
A- Water vapours is lighter than air. Its presence will decrease the density and thus the velocity of sound will increase.
Q-10 What is the effect of temperature on the velocity of sound?
A- The velocity of sound increase with rise in temperature of air. For 1ºC rise in temperature, the increase in velocity of sound is 61 cm/s.
Q-11 What is the effect of density of medium on the velocity of sound?
A- The velocity of sound is inversely proportional to the square root of the density of the medium.It means that the velocity is lesser in denser gases.
Q-12 What are stationary/ standing waves?
A- When two waves of same frequency, amplitude and speed travel along the same line in opposite direction, these waves super impose each other to give rise to stationary waves.
Q-13 Where is node and anti node formed in the vibrating air column in the resonance tube?
A- Node is formed at the closed end i.e. at the surface of the water and anti node is formed little above the open end.
Q-14 Why is it so that anti node is formed a little above the open end?
A- This is due to the fact that sound waves spread out from the open end of the tube. Thisphenomena is called diffraction of sound waves.
Q-15 Under what factors do the production of sound depends?
A- (i) A vibrating body
(ii) A material medium
Q-16 Does the frequency of sound waves change when they enter another medium?
A- No, but their velocity and wavelength do change.
Q-17 Why is water used in the tube?
A- Water serves as denser medium and a node is formed at its surface when air column vibratesin tube.
Q-18 How is a wave reflected?
A- If a transverse wave travelling in a rare medium is incident on denser medium is reflected such that it under goes a phase change of 180º. If a transverse traveling in a denser medium is incidenton a rare medium i.e. is reflected without any change in phase.
Q-19 Does the velocity of sound waves change if the frequency is changed?
A- No, only amplitude changed ( because V= fג)
Q-20 Why do we hear loud sound a resonance?
A- At resonance, amplitude of vibrating air column increase and since loudness depends uponamplitude therefore, we hear a loud sound at resonance.
Q-21 Why should the tuning fork be stuck on a rubber pad at pint near the end?
A- To limit the production of over tones / harmonics.
Q-22 Does the change in diameter of resonance tube affect the velocity of sound?
A- Because it changes only with change of medium.
