Question

Statement$1$ : When a longitudinal pressure wave is reflected at the open end of an organ pipe, the compression pressure wave pulse becomes rare-fraction pressure wave pulse during the reflection.
Statement$2$ : The phase of the wave changes by when reflected at the open end.
A. Both the statements are true and statement $2$is the correct explanation of statement$1$.
B. Both the statements are true but statement $2$ is not the correct explanation of statement –$1$.
C. Statement-$1$ is true and statement -$2$ is false.
D. Statement -$1$ is false and statement -$2$ is true.

Answer 1

Hint: Here, we use the concept of the longitudinal wave propagation and the instruments open at both the ends. Also, considering the pattern of the wave motion consisting the series of the compressions and the rare-factions.

Complete step by step answer:
In the organ pipes, the vibrational anti-nodes would be present at any open end and the vibrational nodes would be present at any closed end. When an organ pipe is played, the air that is pushed (passed) through the pipe it starts vibrating and the standing waves are produced. The longitudinal wave in the air consists of the series of the compressions and the rare-factions moving outward with the velocity v.
So, when the longitudinal pressure wave is reflected at the open end the phase changes by the phase angle pie. Thus the compression becomes the rare- fraction.
Therefore, both the statements true and statement $2$ is the correct explanation of statement$1$

So, the correct answer is “Option A”.

Note:
Keep in mind the different terminologies such as standing waves, longitudinal waves, surface waves and reflection of the waves to solve these types of word problems.