QUESTION 4 Suppose you want to produce a standing wave in a closed tube that has a length of 25 cm. The speed of sound is 340 m/s. What is the smallest possible frequency in Hertz that you can use to produce a standing wave in this tube? QUESTION 6 In order to have a standing wave in an open tube which of the following must be true? O There must be a displacement antinode at the open end of the tube O There must be at least two displacement node close to the middle of the tube There must be a displacement node at the open end of the tube There must be a displacement node in the middle of the tube QUESTION 7 Suppose you want to produce a standing wave in a tube with one end closed and the other end opened that has a length of 50 cm. The speed of sound is 340 m/s. What is the smallest possible frequency in Hertz that you can use to produce a standing wave in this tube