Stationary wavesEdexcel A-Level Physics: Flashcards

Exam questions on Stationary waves

1. A taut wire of length 0.60 m is fixed at both ends and plucked so that it vibrates with a single loop. The wire has a mass per unit length of 4.0 × 10⁻⁴ kg m⁻¹ and is under a tension of 36 N. Treat both fixed ends as nodes.
   The tension is increased to 144 N with the length unchanged. Calculate the new fundamental frequency.2 marks
2. A string is stretched between two fixed points 1.50 m apart. A vibration generator near one end drives the string at 120 Hz, and a stationary wave with exactly three loops is seen between the fixed ends. Treat both ends as nodes.
   Explain how the stationary wave is formed on the string.2 marks
3. A student investigates how the fundamental frequency f of a vibrating string depends on its tension T. A string of vibrating length 0.800 m passes over a pulley and carries hanging masses that provide the tension. For each tension she adjusts the frequency of a vibration generator until the string shows a single loop of maximum amplitude. She plots f² against T and obtains a straight line through the origin with gradient 391 Hz² N⁻¹.
   Use the gradient to determine the mass per unit length of the string.3 marks