Progressive waves and the wave equation
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 1 worked example, 3 practice questions, 5 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Energy without matter
- Progressive waves
Read the transcript of the teaching part
Last time
Before we start: last time, in Phase difference, intensity and the oscilloscope, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Energy without matter
Float a cork on a pond and drop a stone nearby. The ripples spread outwards, but the cork only bobs up and down. The wave carries energy across the water, but the water itself does not travel with it. That is what every progressive wave does.
Progressive waves
A progressive wave is an oscillation that travels, transferring energy from one place to another without transferring matter. This is true for all progressive waves, mechanical or electromagnetic. Electromagnetic waves need no atoms, and cross a vacuum. The source oscillates, and each point along the wave repeats the motion of the source, a little later. A peak-to-trough distance is half a wavelength, not a whole wavelength.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Progressive waves · Transverse and longitudinal waves · Wave equation · Wave terms.
Chapter 7.1: Waves
- Progressive waves and the wave equation 6 min
- Phase difference, intensity and the oscilloscope 6 min
Also for A Level Physics 9702
Which topics come up most in A Level Physics 9702 past papers, counted from every paper since 2004: Paper 1 topic frequency, Paper 2 topic frequency.