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15 Cards in this Set
- Front
- Back
Many electromagnetic waves can be used in communication. Which wave types link with which communication uses? |
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Choose the correct answer.
(a) The shock waves from an earthquake are: A all longitudinal B all transverse C both longitudinal and transverse |
C both longitudinal and transverse |
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Choose the correct answer. (b) Longitudinal waves travel through: A gases only B liquids only C liquids and gases D solids only E solids, liquids and gases |
E solids, liquids and gases |
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Choose the correct answer. (c) The wavelength of a longitudinal wave is the distance between: A a compression and a rarefaction B a crest and a trough C two crests D two rarefactions E two troughs |
D two rarefactions
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What is the difference between a transverse and a longitudinal wave? |
Transverse wave has oscillations perpendicular to the direction of energy transfer. Longitudinal waves have oscillations parallel to the direction of energy transfer. |
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Water waves are passing a breakwater.Each complete wave takes 2.0 s to pass.The distance between two crests is 3 m and the distance between the top of a crest and the bottom of a trough is 90 cm. What is: (i) the frequency of the waves? (ii) the wavelength? |
(i) Frequency = number of waves ÷ time taken = 1 ÷ 2.0 = 0.5 Hz (ii) Wavelength = distance between two crests = 3 m |
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Water waves are passing a breakwater.Each complete wave takes 2.0 s to pass.The distance between two crests is 3 m and the distance between the top of a crest and the bottom of a trough is 90 cm. What is: (iii) the amplitude? (iv) the wave speed? |
(iii) Amplitude = ½ × crest-to-trough distance = 90 ÷ 2 = 45 cm (iv) Wave speed = frequency × wavelength = 0.5 Hz × 3 m = 1.5 m/s |
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When a train approaches, the noise of the rails vibrating can be heard before the train. Explain why this happens. In many science fiction films, missiles and explosions in outer space make loud noises. Explain why this is unrealistic. |
Sound travels faster in metals than through air. Space is a vacuum, or there is nothing, no medium. Sound does not travel through a vacuum, or sound needs a medium to travel though. |
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A time signal for setting radio controlled clocks is broadcast at a frequency of 60 kHz from Cumbria and can be received throughout the UK. (Radio waves travel at a speed of 300 000 000 m/s.) What is the wavelength of the signal? Explain how the signal can be received all over the UK. |
Wavelength = speed ÷ frequency (or 300 000 000 m/s ÷ 60 000 Hz) = 5000 m (or 5 km) The waves will be diffracted between hills or over hills. Because they have a long wavelength/5 km wavelength. This is the same sort of size as the gaps between hills. Diffraction has the biggest effect when wavelength is approximately equal to gap size. |
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A company sells coatings for optical instruments. These graphs show the percentage of the incident radiation reflected at different wavelengths for three coatings: Premier, Choice and Luxcoat. (a) Explain which coating(s) would be suitable for a beam splitter for visible light that transmits half of the beam and reflects the other half. (b) Explain which material would be suitable for a mirror to reflect all visible light. |
(a) Choice because the amount reflected over the range of visible light is about 50%; the other two coatings reflect about 90% of the light for most of the visible range.
(b) Luxcoat because it reflects over 90% for most of the visible range. Choice only reflects 50% and premier only reflects about 55% for part of the visible light range. |
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(c) Explain which material would be suitable as a mirror to reflect infrared radiation. (d) What percentage of the incident light does Choice transmit at 750 nm? (e) Explain whether the coating Luxcoat reflects ultraviolet light. |
(c) Premier because it reflects over 90% in the infrared range. Choice only reflects about 50% and Luxcoat drops to 75% at 800 nm. (d) 45% (e) No, reflection drops to 0% below 380 nm. |
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The data in the Table shows how heavy rainfall can affect the transmission of microwaves with a frequency 15 GHz (1GHz =109 Hz =1 million kHz) and microwaves with a frequency of 39 GHz.
(a) Explain which waves have the longest wavelength. (b) Are there any anomalous results? If so,which ones? (c) What percentage of the energy of the 15GHz waves is left after 1 km when there is no rain? |
(a) The 15 GHz waves, because they have the lowest frequency (or use of speed = frequency × wavelength, speed unchanged). (b) The 15 GHz result for 20 mm/h of 82% is too high. (c) 40% |
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(d) Which frequency is most affected by the rain? (e) A student says that the absorption of the 39 GHz microwaves is proportional to the amount of rain. Explain whether you agree. (f) A microwave signal has to travel 1 km. It can be recovered if 10% of the original energy gets through. Estimate the maximum rainfall rate before the signal is lost if: (i) 15GHz waves or (ii)39GHz waves are used. |
(d) 39 GHz (e) No, zero rain does not give zero absorption OR comparison of values in table to show doubling rainfall rate does not double absorption. (f) (i) 30 mm/h= 88% absorbed and 40 mm/h = 97.5%absorbed. (ii) 10 mm/h= 78% absorbed and 20 mm/h = 96.8%absorbed |
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The Figure shows waves entering a harbour.This effect is called: A diffraction B dispersion C reflection D refraction. |
A diffraction |
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Compare how a terrestrial TV signal from a transmitter reaches your TV set with how a satellite TV signal reaches it. |
A terrestrial TV signal is broadcast from a transmitter using radio waves. It diffracts round hills and reaches the TV aerial. A satellite TV signal is sent to the satellite from a transmitter using microwaves. It is retransmitted by the satellite to Earth and reaches the satellite dish. |
