Sound — task. Physics CBSE Live product, Class 9 (2026-27).

Choose the correct answer:

1. A laboratory produces four sounds with frequencies of \(10\ Hz\), \(500\ Hz\), \(18,000\ Hz\) and \(30,000\ Hz\). Which option correctly classifies all four sounds?

\(10\ Hz\) – audible; \(500\ Hz\) – audible; \(18,000\ Hz\) – infrasonic; \(30,000\ Hz\) – ultrasonic
\(10\ Hz\) – infrasonic; \(500\ Hz\) – audible; \(18,000\ Hz\) – audible; \(30,000\ Hz\) – ultrasonic
\(10\ Hz\) – audible; \(500\ Hz\) – infrasonic; \(18,000\ Hz\) – ultrasonic; \(30,000\ Hz\) – audible
\(10\ Hz\) – ultrasonic; \(500\ Hz\) – audible; \(18,000\ Hz\) – infrasonic; \(30,000\ Hz\) – ultrasonic

2. A violin and a flute produce the same musical note at approximately the same loudness. A listener can still distinguish which instrument produced the sound. Which property best explains this observation?

Speed of sound alone, because the sound travels at a different speed from every instrument
Amplitude alone, because loudness determines the identity of an instrument
Frequency alone, because every instrument producing the same note must have exactly the same waveform
Timbre, because different instruments can produce different combinations of fundamental frequency and overtones

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1. Sound

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