Monthly Archives: April 2009

Sound

Sound waves are longitudinal vibrations which produce pressure waves. In dense materials, sound travels faster than in less dense materials, because the vibrating molecules push against others closer to them, so energy is transmitted more quickly. We usually hear sound … Continue reading

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Electromagnetic Spectrum – The Whole Nine Yards

We know already that all EM waves are transverse electromagnetic oscillations, travelling at 300 million m/s in free space. We also know that a glass block slows them down to about 200 million m/s. We can only see a little … Continue reading

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Electromagnetic Spectrum – IR and UV

The light that we can see (from red to violet) is only a tiny fraction of a family of transverse electromagnetic oscillations. Beyond the red – the infrared, at longer wavelengths than visible light. All bodies above absolute zero emit … Continue reading

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Hawking’s non-eventual Universe

Stephen Hawking is ill, poor man and hospitalised in Cambridge. My imagination is caught by quantum cosmology, the notion that representing the Universe as one of many by a probabilistic wavefunction might or might not be at least a partial … Continue reading

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How Lenses Work

We all know about refraction. Light changes speed and maybe direction as it goes from (say) air to glass. If the glass is a particular curved shape, we can determine the direction of the refracted rays and get them to … Continue reading

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Dispersion and Rainbows

White light, so-called, isn’t really white, but a mixture of red, yellow, green, blue, indigo and violet. It can be dispersed or spread out by a triangular prism. ┬áRead Out Your Good Book In Verse, alternatively Richard Of York Gave … Continue reading

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Optical Fibres – total internal reflection

Suppose you want to shine a torch beam down a long, straight hallway. Just point the beam straight down the hallway – light travels in straight lines, so there’s no problem. What if the hallway has a bend in it? … Continue reading

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