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1 of 28 © Boardworks Ltd 2006
Multiple-choice quiz
2 of 28 © Boardworks Ltd 2006
Simulation of a transverse wave
3 of 28 © Boardworks Ltd 2006
The wavelength of any wave is the distance between two matching points on neighbouring waves.
Wavelength of a transverse wave
The wavelength is the same whichever two matching points are used to measure this distance.
wavelength
wavelength
wavelength
The symbol used to represent wavelength is .
4 of 28 © Boardworks Ltd 2006
The amplitude of any wave is the maximum distance a point moves from its rest position.
Amplitude of a transverse wave
The amplitude of a transverse wave is the height of a peak or trough from the wave’s rest position of the wave.
amplitude
amplitude
The larger the amplitude, greater the energy of the wave.
5 of 28 © Boardworks Ltd 2006
Investigating transverse waves
6 of 28 © Boardworks Ltd 2006
Frequency of waves – activity
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Simulation of a longitudinal wave
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Transverse or longitudinal waves?
9 of 28 © Boardworks Ltd 2006
Total internal reflection – simulation
10 of 28 © Boardworks Ltd 2006
Optical fibres are thin strands of solid glass, about the size of a human hair.
What are optical fibres?
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.
11 of 28 © Boardworks Ltd 2006
Why are optical fibres so important?
12 of 28 © Boardworks Ltd 2006
Optical fibres do not have to be straight to carry light and can even carry light around corners.
How do optical fibres carry light?
Light travels through the Perspex rod, and optical fibres, by aprocess called total internal reflection.
This curved Perspex rod shows how light travels in an optical fibre.
13 of 28 © Boardworks Ltd 2006
What is total internal reflection?
A ray of light enters the optical fibre.
light enters optical fibre
light leaves 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.
14 of 28 © Boardworks Ltd 2006
What’s in a cable of optical fibres?
15 of 28 © Boardworks Ltd 2006
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.
How are optical fibres used in medicine?
Light is sent down some of the fibres and the image is reflected back through the other fibres.
16 of 28 © Boardworks Ltd 2006
Optical fibres – true or false?
17 of 28 © Boardworks Ltd 2006
Multiple-choice quiz