A Blu-ray disc (BD) is used to record and store high-definition digital information.
Describe the differences between analogue and digital signals. You may draw a diagram to support your answer.
The diagram shows an enlarged cross-section of a Blu-ray disc.
Light is emitted from the laser. It is then reflected from the reflective layer of the Blu-ray disc and received at the detector.
The equation linking average speed, distance moved and time taken is:
average speed=distance movedtime taken \text{average speed} = \frac{\text{distance moved}}{\text{time taken}} average speed=time takendistance movedThe distance between the reflective layer and the laser is 1.8 mm1.8\text{ mm}1.8 mm.
The laser light travels at an average speed of 2.4×108 m/s2.4 \times 10^8\text{ m/s}2.4×108 m/s between the laser and the detector.
Calculate the time taken for the laser light to be received at the detector after it is emitted from the laser.
A moving-coil microphone is used to record the acoustic sound of music so it can be stores on a digital medium.
The diagram shows the construction of this microphone.
Explain how the moving-coil microphone produces an electrical signal from a sound wave.
