. VELOCITY OF SOUND IN AIR USING RESONANCE COLUMN AIM To determine the velocity of sound in air at room temperature using the resonance phenomenon. APPARATUS REQUIRED Resonance tube, three tuning forks of known frequencies, a rubber hammer, one thermometer, plumb line, set squares, water in a beaker. FORMULA v l l m s - where V → Speed of sound in air (m s - ) l and l → The length of the air column for the first and second resonance respectively (m) v → Frequency of the tuning fork (Hz) DIAGRAM B B D B D D l1 l2 Iron base Rubber tube water reservoir PROCEDURE ¾ Adjust the position of the resonance tube, so that the length of air column inside the tube is very small.
¾ Take a tuning fork of known frequency and strike it with a rubber hammer. The tuning fork now produces longitudinal waves with a frequency equal to the natural frequency of the tuning fork. ¾ Place the vibrating tuning fork horizontally at the open end of the resonance tube. Sound waves pass down the total tube and reflect back at the water surface.
¾ Length of the water column in the tube is adjusted either by lowering or raising the reservoir or the tube, until a maximum sound(resonance) occurs. ¾ Measure the length of air column at this position. This is taken as the first resonating length, l UNIT- (XI- - ) PRACTICAL FIRST UNIT- (XI- - ) PRACTICAL FIRST - - - - Practical ¾ Then raise the tube approximately about two times the first resonating length. Excite the tuning fork again and place it on the open end of the tube.
¾ Adjust the height of the air column until the maximum sound is heard. ¾ Measure the length of air column at this position. This is taken as the second resonating length l ¾ We can now calculate the velocity of sound in air at room temperature by using the relation. V = v ( l − l ) ¾ Repeat the experiment with tuning forks of different frequency and tabulate the corresponding values of l and l .
¾ The mean of the calculated values will give the velocity of sound in air at room temperature. OBSERVATIONS Sl. No. Frequency of tuning fork ' v ' (Hz) First resonating length l (× − m ) Second resonating length l (× − m ) l − l (× − m ) Velocity of sound V = v ( l − l ) (m s - ) Trial Trial Mean Trial Trial Mean Mean V = CALCULATION Velocity sound in air at room temperature, V = v ( l − l ) = m s - RESULT Velocity of sound in air at room temperature, is found to be (V) = m s - UNIT- (XI- - ) PRACTICAL FIRST UNIT- (XI- - ) PRACTICAL FIRST - - - - Practical