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17 Cards in this Set
- Front
- Back
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State three properties that we use to describe waves.
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Waves can be described by their amplitude, wavelength and frequency.
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How can the speed of a wave be calculated? |
The speed of a wave can be calculated from its frequency and wavelength. |
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Explain amplitude. |
The amplitude of a wave is its maximum disturbance from its undisturbed position.
The amplitude is not the distance between the top and bottom of a wave. |
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Explain wavelength. |
The wavelength of a wave is the distance between a point on one wave and the same point on the next wave. It is often easiest to measure this from the crest of one wave to the crest of the next wave, but it doesn't matter where as long as it is the same point in each wave.
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Explain frequency. |
The frequency of a wave is the number of waves produced by a source each second. It is also the number of waves that pass a certain point each second. |
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What is the unit of frequency? |
The unit of frequency is the hertz (Hz).
It is common for kilohertz (kHz), megahertz (MHz) and gigahertz (GHz) to be used when waves have very high frequencies. |
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What is rarefaction? What is compression? |
Rarefaction is where particles are spread out. Compression is where particles are squashed together. Longitudinal waves show areas of compression and rarefaction. |
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How do we calculate the speed of a wave? |
The speed of a wave is related to its frequency and wavelength, according to this equation: v = f × λ v is the wave speed in metres per second, m/s f is the frequency in hertz, Hz λ (lambda) is the wavelength in metres, m. |
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Ten waves pass a point on a rope in 4 s. What is their frequency? |
10 waves ÷ 4 s = 2.5 Hz.¸ |
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Five waves measure 25 cm and pass a point in 1 s. What is:
(a) the wavelength? (b) the frequency? |
(a) 25 cm ÷ 5 waves = 5 cm (b) 5 waves ÷ 1 s = 5 Hz (or 25 cm/s ¸ 5 cm = 5 Hz) |
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Waves in a spring have a frequency of 8 Hz and a travel at a speed of 4 m/s. What is their wavelength? |
4 m/s ÷ 8 Hz = 0.5 m |
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Light waves have a wavelength of 0.0000005 m and a frequency of 600 000 000 000 000 Hz. What is the speed of light? |
0.000 000 5 m × 600 000 000 000 000 Hz = 300 000 000 m/s. |
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Water waves with wavelength 1.5 cm travel across a tank at 0.021 m/s. What is their frequency? |
1.5 cm = 0.015 m, 0.021 m/s ÷ 0.015 m = 1.4 Hz |
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If the frequency of waves is doubled what happens to: (a) the wave speed? (b) the wavelength? |
(a) The wave speed stays the same. (b) The wavelength halves. |
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Longitudinal waves travel through steel at 6000 m/s. If the frequency is 2000 Hz what is the distance between the centre of a compression and the centre of a rarefaction? |
Wavelength = 6000 m/s ÷ 2000 Hz = 3 m, distance = ½ wavelength = 1.5 m |
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Draw a diagram of a transverse wave and use it to explain what is meant by the wavelength, amplitude, frequency and wave speed of a wave, and the units each of these are measured in. |
Wave speed is the speed at which the wave travels through the medium; wave speed is measured in m/s Wavelength is the distance for one whole wave, or crest to crest; wavelength is measured in metres Frequency is number of waves/cycles per second and is measured in hertz. |
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What are the key points to remember? |
The frequency of a wave is the number of cycles per second. Frequency is measured in hertz (Hz). The wavelength is the length of one complete wave. The amplitude is the maximum displacement. ν = f × λ wave speed = frequency × wavelength. The wave speed depends on the medium. |
