Superposition and stationary wavesAQA A-Level Physics: Flashcards

Exam questions on Superposition and stationary waves

1. Two wave pulses travel towards each other along a long stretched rope. One is a crest with a maximum displacement of 0.040 m, and the other is a crest with a maximum displacement of 0.030 m, both on the same side of the undisturbed rope. The pulses overlap exactly at one instant and then move apart.
   State the principle of superposition and use it to describe what happens to the two original pulses after they have passed through each other.2 marks
2. A guitar string is fixed at both ends and the vibrating length is 0.65 m. The string has mass per unit length 5.0 × 10⁻³ kg m⁻¹ and is under a tension of 80 N. It is plucked so that it vibrates in its first harmonic.
   The tension is increased to 320 N, with the length and mass per unit length unchanged. Calculate the new frequency of the first harmonic.2 marks
3. A microwave transmitter faces a flat metal plate, 0.50 m away, and sets up a stationary wave between the transmitter and the plate. A small microwave detector is moved slowly along the line between them and the signal is found to fall to a minimum at positions that are 1.4 cm apart. The speed of electromagnetic waves is 3.00 × 10⁸ m s⁻¹.
   Explain how a stationary wave is formed between the transmitter and the plate.3 marks