A laboratory timing system sends visible-light pulses along two paths.
One pulse travels 0.90 m through a transparent polymer at 2.0 × 108 m/s. The other pulse travels 1.20 m through a vacuum at 3.0 × 108 m/s.
The pulses must reach the ends of their paths at the same time. Use t=d/vt=d/vt=d/v.
Which timing adjustment should the system make?
Delay the vacuum-path pulse by 1.0×10−9 s1.0\times10^{-9}\ \mathrm{s}1.0×10−9 s
Delay the polymer-path pulse by 1.0×10−9 s1.0\times10^{-9}\ \mathrm{s}1.0×10−9 s
Delay the polymer-path pulse by 5.0×10−10 s5.0\times10^{-10}\ \mathrm{s}5.0×10−10 s
Delay the vacuum-path pulse by 5.0×10−10 s5.0\times10^{-10}\ \mathrm{s}5.0×10−10 s
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.