Definitions and Equations (GCSE Recap)

Overview

This lesson rebuilds the wave language needed for AS Physics. You should be able to describe what is moving, what is being transferred, and how a wave diagram or graph gives the quantities needed for a calculation.

What You Need to Know

• A progressive wave transfers energy from one place to another while the particles or fields oscillate.
• Displacement is measured from the equilibrium position. Amplitude is the maximum displacement.
• Period is the time for one complete oscillation. Frequency is the number of oscillations per second, so f = 1 / T.
• Wavelength is the distance between two adjacent points in phase, such as crest to crest or compression to compression.
• The wave equation v = f lambda follows from one wavelength passing a point every period.
• In transverse waves, oscillations are perpendicular to the direction of energy transfer. In longitudinal waves, oscillations are parallel to the direction of energy transfer.

How to Work Through It

1. Start by matching wave terms to symbols, units, and positions on a diagram.
2. Use rope, spring, or ripple-tank examples to separate particle motion from wave energy transfer.
3. Derive v = f lambda, then use it in short calculation questions.
4. Compare transverse and longitudinal diagrams, including displacement-distance and displacement-time graphs.

Check Your Understanding

• Which quantity is read from the vertical axis on a displacement graph?
• How do you know whether two points on a wave are in phase?
• Why is wave speed not the same thing as particle speed?
• What changes in v = f lambda if the frequency is doubled in the same medium?

Common Mistakes

• Treating the particles in the medium as if they travel along with the wave.
• Confusing a displacement-time graph with a displacement-distance graph.
• Using amplitude where wavelength is needed in the wave equation.
• Describing longitudinal waves as “up and down” instead of parallel to the direction of travel.

Next Steps

• Complete the wave equation and definitions practice from the lesson resource.
• Bring the graph-reading skills forward into the oscilloscope lesson.