Name: Stationary Wave in Closed and Open Organ Pipe
Uploaded: 2019-07-19
Duration: 11 min 39 s
Description: Organ pipes are musical instruments that produce a musical sound by blowing air into the pipe. Let's study the formation of stationary waves in organ pipes.

Question

Explain the principle for determining the speed of sound in a gas by Quincke&rsquo;s tube and state the formula used.

Accepted Answer

lt consists of two U-shaped tubes B and C. The tube B can be slided inside the tube C and the distance can be read on a scale. Two small tubes A and D are attached at right angles to the tube B. A Galton’s whistle is put before the opening of the tube I and a sensitive flame before the opening of the tube D.
When the whistle is blown, the sound waves enter the tube A and are divided into two parts. These parts travel along the paths ABD and ACD and reach the tube D where they Interfere. If both the paths are exactly equal then the waves will reach the tube D in the same phase. Hence, the sound intensity in the tube D will be maximum and the sensitive flame will flicker violently and became shortened. Now, if the tube C is moved slowly outward, the path ACD Increases.When this tube is slid by a distance $\frac{λ}{4}$ , the length of the path ACD increases by $\frac{λ}{2}$ , that is, the path difference between the two waves becomes $\frac{λ}{2}$ . Hence, now the waves meet in opposite phases and the sound intensity in the tube D becomes nearly zero. In this state the sensitive flame becomes calm and acquires the same length as before.If the tube C is further moved by distance $\frac{λ}{4}$ , the path difference between the waves will become $λ$ , Again the waves will meet in the same phase and the sound intensity will again be maximum. Hence, the sensitive flame will again flicker violently and be shortened. Thus, by moving the tube C outward, a number of positions can be obtained in which the sound intensity in the tube D is either maximum or minimum. The distance through which the tube C is moved between two positions of minimum sound intensity calm flame)is $\frac{λ}{2}$ . Thus, $λ$ is determined.

Explain the principle for determining the speed of sound in a gas by Quincke’s tube and state the formula used.

Important Questions on Superposition of Waves-1 : Interference and Beats

Learn and Prepare for any exam you want !