NTA Abhyas JEE Main2020PhysicsWaves and SoundPractice
In an organ pipe whose one end is at x = 0 , the pressure is expressed by p = p 0 cos 3 π x 2 sin 3 0 0 π t where x is in meter and t in seconds. The organ pipe can be
Options
- AClosed at one end, open at another with length =   0 . 5   m
- BOpen at both ends, length = 1   m
- CClosed at both ends, length = 2   m
- DClosed at end, open at another with length = 2 3   m
Correct answer
C. Closed at both ends, length = 2   m
Step-by-step solution
For x = λ 3 π x 2 = 2 π ⇒ λ = 4 3 at x = 0 there is a pressure antinode. So first end must be close and in case of close at bot end l = n λ 2 ⇒ l = 2 n 3 for close at one end l = 2 n + 1 λ 4 = 2 n + 1 3 So for close at one end possible lengths are 2 n + 1 3 = 1 3 , 1 , 5 3 , 7 3 Open at both ends is not possible for close at both end possible length are 2 n 3 = 2 3 , 4 3 , 2 , 8 3 ...... so only possibility is (3)