In a laboratory, a pulse of laser light travels along a glass optical fibre and then across a tank of water to a detector. The detector only records a pulse that arrives within 1.8 × 10-8 s of the laser producing it.
| Section of the path | Distance travelled | Wave speed of the light |
|---|---|---|
| glass optical fibre | 3.0 m | 2.0 × 108 m/s |
| water in the tank | 0.45 m | 2.25 × 108 m/s |
Use t=d/vt=d/vt=d/v.
Calculate the time the pulse takes to reach the detector and state whether the detector records the pulse.
84 exam-style questions on Edexcel GCSE Physics 5.2 The electromagnetic spectrum, covering 5.2.1 Electromagnetic waves and refraction in glass (core practical), 5.2.2 Groups of the electromagnetic spectrum, 5.2.3 Wavelength-dependent behaviour of EM waves, and 5.2.4 Velocities of EM waves in different substances. Each one has a worked solution and a mark scheme showing where the marks go.