Assertion (A): Compressions and rarefactions move through the medium. Reason (R): Individual particles of the medium continuously move forward with the wave.
Explanation
Assertion (A) is true because the textbook context clearly states that compressions and rarefactions are produced alternately and travel away from the source, moving ahead through the medium. However, Reason (R) is false. The context explicitly mentions that the particles themselves 'oscillate only about their mean positions' and that the disturbance propagates 'without the actual flow of the particles of medium'. Therefore, individual particles do not continuously move forward with the wave. Since A is true and R is false, option (iii) is the correct choice.
Solution Steps
Step 1: Evaluate Assertion (A). The context states that compressions and rarefactions 'travel away from the source' and 'moves ahead', confirming that A is true.
Step 2: Evaluate Reason (R). The context states that 'the particles themselves oscillate only about their mean positions' and 'the air particles themselves do not travel with it', confirming that R is false.
Step 3: Match the truth values with the given options. Since A is true and R is false, the correct statement is option (iii).