Monthly Archives: October 2008

Centre of Mass (or Gravity)

Imagine you could squash a pool ball up to the size of a pinhead. An arrow drawn vertically downwards from that point shows the centre of gravity, acting at the centre of mass. Where might the centre of gravity of … Continue reading

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Ladders and Tramlines: Electrons as waves and particles

What’s an eV? eV stands for electron volt – that is, the amount of energy needed to move one electron through a potential difference of one volt. If that doesn’t mean much to you, don’t worry about it; the point is … Continue reading

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Polarisation (Polarization)

If a wave is plane polarised, all the oscillation directions except one are absorbed. This can only happen with transverse oscillations since these are oscillations at right angles to the direction of travel and there are lots of ways for … Continue reading

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The Inverse Square Law

    This works for all waves but it’s convenient to think about EM waves. Imagine a point source of EM wave energy, such as a candle, a light bulb or even the Sun, radiating energy in all directions. We … Continue reading

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Waves within Boundaries : Strings

A guitar string is fixed at both ends. If we pluck a guitar string in the middle, near the twelfth fret, the string oscillates with SHM. The tension and mass per unit length defines how fast the string moves in … Continue reading

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Huygens and Single Slit Diffraction

Huygens’ Constructions are geometric diagrams which aren’t in the A2 specification, but they’re a fast way of getting to grips with several progressive wave properties like reflection, refraction, diffraction and interference, particularly with EM waves, but modelled in a ripple … Continue reading

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Additional thoughts about Interference and Diffraction

Interference happens when wave amplitudes add together algebraically in space and time. This is a fancy way of saying that if two waves/pulses/ripples meet, their amplitudes add up at a particular place and a particular moment. When two crests meet, … Continue reading

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