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24. Medical physics
A section of Physics, 9702
Listing 10 of 162 questions
One channel of communication is by the use of a coaxial cable. Such a cable is illustrated in . A inner copper wire plastic insulation protective covering Suggest the material from which the component labelled A on is made. Suggest two functions of the component labelled A. 1. 2. When a signal travels along the coaxial cable, it is attenuated. State the meaning of attenuation. State and explain why attenuation is frequently measured in decibels (dB). A television aerial is connected to a receiver using a coaxial cable of length 11 m. The attenuation per unit length of the cable is 190 dB km–1. Calculate the ratio output signal from coaxial cable input signal to coaxial cable . ratio = Please for Question 12.
9702_s15_qp_42
THEORY
2015
Paper 4, Variant 2
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The digital transmission of speech may be illustrated using the block diagram of . ADC serial -to - parallel converter optic fibre X Y State what is meant by a digital signal. State the names of the components labelled X and Y on . X: Y: Describe the function of the ADC. The optic fibre has length 84 km and the attenuation per unit length in the fibre is 0.19 dB km–1. The input power to the optic fibre is 9.7 mW. At the output from the optic fibre, the signal-to- noise ratio is 28 dB. Calculate in dB, the ratio input power to optic fibre noise power at output of optic fibre, ratio = dB the noise power at the output of the optic fibre. noise power = W
9702_s17_qp_41
THEORY
2017
Paper 4, Variant 1
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The digital transmission of speech may be illustrated using the block diagram of . ADC serial -to - parallel converter optic fibre X Y State what is meant by a digital signal. State the names of the components labelled X and Y on . X: Y: Describe the function of the ADC. The optic fibre has length 84 km and the attenuation per unit length in the fibre is 0.19 dB km–1. The input power to the optic fibre is 9.7 mW. At the output from the optic fibre, the signal-to- noise ratio is 28 dB. Calculate in dB, the ratio input power to optic fibre noise power at output of optic fibre, ratio = dB the noise power at the output of the optic fibre. noise power = W
9702_s17_qp_43
THEORY
2017
Paper 4, Variant 3
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The output of a microphone is processed using a non-inverting amplifier. The amplifier incorporates an operational amplifier (op-amp). State, by reference to the input and output signals, the function of a non-inverting amplifier. The circuit for the microphone and amplifier is shown in . 15 kΩ 2.0 kΩ R P VOUT – + +5 V –5 V The output potential difference VOUT is 2.6 V when the potential at point P is 84 mV. Determine: the gain of the amplifier circuit gain = the resistance of resistor R. resistance = Ω For the circuit of : suggest a suitable device to connect to the output such that the shape of the waveform of the sound received by the microphone may be examined state and explain the effect on the output potential difference VOUT of increasing the resistance of resistor R.
9702_s20_qp_41
THEORY
2020
Paper 4, Variant 1
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The output of a microphone is processed using a non-inverting amplifier. The amplifier incorporates an operational amplifier (op-amp). State, by reference to the input and output signals, the function of a non-inverting amplifier. The circuit for the microphone and amplifier is shown in . 15 kΩ 2.0 kΩ R P VOUT – + +5 V –5 V The output potential difference VOUT is 2.6 V when the potential at point P is 84 mV. Determine: the gain of the amplifier circuit gain = the resistance of resistor R. resistance = Ω For the circuit of : suggest a suitable device to connect to the output such that the shape of the waveform of the sound received by the microphone may be examined state and explain the effect on the output potential difference VOUT of increasing the resistance of resistor R.
9702_s20_qp_43
THEORY
2020
Paper 4, Variant 3
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11 Wire pairs provide one means of communication but they are subject to high levels of noise and attenuation. Explain what is meant by noise, attenuation. A microphone is connected to a receiver using a wire pair, as shown in . receiver wire pair microphone The wire pair has an attenuation per unit length of 12 dB km–1. The noise power in the wire pair is 3.4 × 10–9 W. The microphone produces a signal power of 2.9 lW. Calculate the maximum length of the wire pair so that the minimum signal-to-noise ratio is 24 dB. length = m Communication over distances greater than that calculated in is required. Suggest how the circuit of may be modified so that the minimum signal-to-noise ratio at the receiver is not reduced.
9702_w10_qp_41
THEORY
2010
Paper 4, Variant 1
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11 Wire pairs provide one means of communication but they are subject to high levels of noise and attenuation. Explain what is meant by noise, attenuation. A microphone is connected to a receiver using a wire pair, as shown in . receiver wire pair microphone The wire pair has an attenuation per unit length of 12 dB km–1. The noise power in the wire pair is 3.4 × 10–9 W. The microphone produces a signal power of 2.9 lW. Calculate the maximum length of the wire pair so that the minimum signal-to-noise ratio is 24 dB. length = m Communication over distances greater than that calculated in is required. Suggest how the circuit of may be modified so that the minimum signal-to-noise ratio at the receiver is not reduced.
9702_w10_qp_42
THEORY
2010
Paper 4, Variant 2
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Questions Discovered
162