Practice question

Given: A string fixed at both ends has a length of 1.4 m and a wave speed of 70 m/s. What is the frequency of its second harmonic? These values define the system as per NCERT data. Formula: For fixed ends: v_n = n v/2L. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Second harmonic ( n = 2 ): v_2 = 2 × 70/2 × 1.4 = 140/2.8 = 50 Hz . Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m/s², 10⁻⁵ are properly used as per NCERT.