Question

A person blows into open-end of a long pipe. As a result, a high-pressure pulse of air travels down the pipe. When this pulse reaches the other end of the pipe,

• A. a high-pressure pulse starts travelling up the pipe, if the other end of the pipe is open
• B. a low-pressure pulse starts travelling up the pipe, if the other end of the pipe is open
• C. a low-pressure pulse starts travelling up the pipe, if the other end of the pipe is closed
• D. a high-pressure pulse starts travelling up the pipe, if the other end of the pipe is closed

Answer 1

Answer: (D)

a high-pressure pulse starts travelling up the pipe, if the other end of the pipe is closed

Answer 2

At open end phase of pressure wave changes by 180$^{\circ}$. So, compression returns as rarefaction. At closed end there is no phase change. So, compression returns as compression and rarefaction as rarefaction.