IGCSE 0625 · WAVES · 3.1

General properties of Waves

One map of the whole sub-topic: how we describe a wave, the wave equation, transverse and longitudinal waves, and how waves reflect, refract, and diffract. Core ideas are linked in teal and blue, Extended ideas in green and violet.

TOPIC 3.1: GENERAL PROPERTIES OF WAVES CAMBRIDGE IGCSE PHYSICS SYLLABUS · PATHWAYS TheLucidSTEM · thelucidstem.com CORE CORE EXTENDED EXTENDED GENERAL PROPERTIES OF WAVES DESCRIBING A WAVE wavelength λ amplitude crest trough A wave transfers energy without moving matter. Wavefront: a line joining points in step. Frequency f: waves passing per second, in Hz. Wave speed v: how fast the wavefront travels. WAVE MOTION vibration energy travels this way Shown by ropes and springs, and by a ripple tank for water waves. TRANSVERSE vs LONGITUDINAL Transverse: vibration at 90° to the travel. e.g. light, water, all EM Longitudinal: vibration along the travel. compression rarefaction e.g. sound, seismic P-waves KEY EQUATIONS v = f λ v wave speed (m/s) f frequency (Hz) λ wavelength (m) f = 1 / T T is the period (s) one period T displacement vs time WAVE BEHAVIOUR Reflection at a plane surface i r i = r Refraction: speed changes at a boundary glass Bends toward the normal, f stays the same. Diffraction: spreading through a gap Waves bend and spread out. THE RIPPLE TANK EXTENDED A ripple tank demonstrates all three behaviours of water waves. straight wavefronts from a vibrating bar Reflection off a straight barrier. Refraction over a shallow region where the waves slow down. Diffraction through a gap or around an edge. Frequency is set by the dipper. DIFFRACTION: GAP AND EDGE EXTENDED gap wider than λ little spreading gap about λ strong spreading At an edge bends round the edge Diffraction is greatest when the gap is about one wavelength. The wavelength does not change when a wave diffracts. Only the direction and spreading of the wavefronts change.
TOPIC 3.1: GENERAL PROPERTIES OF WAVES CAMBRIDGE IGCSE PHYSICS SYLLABUS · PATHWAYS TheLucidSTEM · thelucidstem.com CORE CORE EXTENDED EXTENDED GENERAL PROPERTIES OF WAVES DESCRIBING A WAVE wavelength λ amplitude crest trough A wave transfers energy without moving matter. Wavefront: a line joining points in step. Frequency f: waves passing per second, in Hz. Wave speed v: how fast the wavefront travels. WAVE MOTION vibration energy travels this way Shown by ropes and springs, and by a ripple tank for water waves. TRANSVERSE vs LONGITUDINAL Transverse: vibration at 90° to the travel. e.g. light, water, all EM Longitudinal: vibration along the travel. compression rarefaction e.g. sound, seismic P-waves KEY EQUATIONS v = f λ v wave speed (m/s) f frequency (Hz) λ wavelength (m) f = 1 / T T is the period (s) one period T displacement vs time WAVE BEHAVIOUR Reflection at a plane surface i r i = r Refraction: speed changes at a boundary glass Bends toward the normal, f stays the same. Diffraction: spreading through a gap Waves bend and spread out. THE RIPPLE TANK EXTENDED A ripple tank demonstrates all three behaviours of water waves. straight wavefronts from a vibrating bar Reflection off a straight barrier. Refraction over a shallow region where the waves slow down. Diffraction through a gap or around an edge. Frequency is set by the dipper. DIFFRACTION: GAP AND EDGE EXTENDED gap wider than λ little spreading gap about λ strong spreading At an edge bends round the edge Diffraction is greatest when the gap is about one wavelength. The wavelength does not change when a wave diffracts. Only the direction and spreading of the wavefronts change.
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