Superposition, coherence and interferenceEdexcel A-Level Physics: Flashcards

Exam questions on Superposition, coherence and interference

1. Two identical loudspeakers are connected to the same signal generator, which produces a sine wave of frequency 850 Hz. They face a listener in a large room with sound-absorbing walls. The speed of sound in air is 340 m s⁻¹.
   Calculate the phase difference, in radians, between the two waves at a point where the path difference is 0.10 m.2 marks
2. Two small dippers, fixed to the same motor, vibrate in a shallow tank of water at 12 Hz. Each dipper produces circular ripples that travel at 0.18 m s⁻¹. A point P on the water surface is 12.0 cm from dipper A and 15.0 cm from dipper B.
   Dipper B is replaced by one that vibrates exactly in antiphase with dipper A, at the same frequency. Explain what is now observed at P.2 marks
3. A car radio receives a 100 MHz FM signal both directly from a transmitter and by reflection from a tall building. The speed of radio waves is 3.00 × 10⁸ m s⁻¹. At one position on the road the reflected signal has travelled 4.5 m further than the direct signal. Ignore any phase change on reflection.
   Calculate the wavelength of the signal and the phase difference between the direct and reflected signals at this position. State the effect on the received signal.3 marks