Physics · Wave behaviour. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
A travelling wave transfers energy from place to place without transferring matter. The particles of the medium only oscillate about fixed positions. In a transverse wave they oscillate at right angles to the direction of energy transfer. In a longitudinal wave they oscillate parallel to it, making compressions (high pressure) and rarefactions (low pressure).
Sound is a longitudinal mechanical wave, so it needs a medium. Electromagnetic waves are transverse oscillations of electric and magnetic fields. They need no medium and all travel at 3.0 × 108 m s−1 in a vacuum.
Read wave graphs with care. A displacement–distance graph shows the wavelength. A displacement–time graph shows the period of one point.
Students read the wavelength from a displacement–time graph. Check the horizontal axis first: time gives the period, distance gives the wavelength.
Answer: About 1.4 m.
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