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Multiple-choice quiz 1 of 28 © Boardworks Ltd 2006 Simulation of a transverse wave 2 of 28 © Boardworks Ltd 2006 Wavelength of a transverse wave The wavelength of any wave is the distance between two matching points on neighbouring waves. wavelength wavelength wavelength The wavelength is the same whichever two matching points are used to measure this distance. The symbol used to represent wavelength is . 3 of 28 © Boardworks Ltd 2006 Amplitude of a transverse wave The amplitude of any wave is the maximum distance a point moves from its rest position. amplitude amplitude The amplitude of a transverse wave is the height of a peak or trough from the wave’s rest position of the wave. The larger the amplitude, greater the energy of the wave. 4 of 28 © Boardworks Ltd 2006 Investigating transverse waves 5 of 28 © Boardworks Ltd 2006 Frequency of waves – activity 6 of 28 © Boardworks Ltd 2006 Simulation of a longitudinal wave 7 of 28 © Boardworks Ltd 2006 Transverse or longitudinal waves? 8 of 28 © Boardworks Ltd 2006 Total internal reflection – simulation 9 of 28 © Boardworks Ltd 2006 What are optical fibres? Optical fibres are thin strands of solid glass, about the size of a human hair. They are widely used in communication, medicine, lighting and as sensors. The first transatlantic telephone cable to use optical fibres went into operation in 1988. Optical fibres can transmit light signals at high speed over long distances and are used in phone and internet connections. 10 of 28 © Boardworks Ltd 2006 Why are optical fibres so important? 11 of 28 © Boardworks Ltd 2006 How do optical fibres carry light? Optical fibres do not have to be straight to carry light and can even carry light around corners. This curved Perspex rod shows how light travels in an optical fibre. Light travels through the Perspex rod, and optical fibres, by a process called total internal reflection. 12 of 28 © Boardworks Ltd 2006 What is total internal reflection? A ray of light enters the optical fibre. As the light enters the optical fibre, it is refracted. This means that the direction the light is travelling in changes. The ray of light hits the wall of the fibre and is totally internally reflected when the angle of incidence is greater than the critical angle. The ray of light passes down the optical fibre by repeated total internal reflection. 13 of 28 light enters optical fibre light leaves optical fibre © Boardworks Ltd 2006 What’s in a cable of optical fibres? 14 of 28 © Boardworks Ltd 2006 How are optical fibres used in medicine? Optical fibres can be used by doctors to look inside a patient’s body without having to cut them open to check that they are healthy. The device used for this purpose is called an endoscope. It contains a bundle of optical fibres that are held together and can be inserted into the body. Light is sent down some of the fibres and the image is reflected back through the other fibres. 15 of 28 © Boardworks Ltd 2006 Optical fibres – true or false? 16 of 28 © Boardworks Ltd 2006 Multiple-choice quiz 17 of 28 © Boardworks Ltd 2006