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Questions and Answers
The wavelength of red light in air is ______ mm.
The wavelength of red light in air is ______ mm.
0.75
In a coaxial or fiber-optic cable, the wavelength is shorter at ______ μm.
In a coaxial or fiber-optic cable, the wavelength is shorter at ______ μm.
0.5
A sine wave is defined by its amplitude, frequency, and ______.
A sine wave is defined by its amplitude, frequency, and ______.
phase
The time-domain plot shows changes in signal amplitude with respect to ______.
The time-domain plot shows changes in signal amplitude with respect to ______.
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A frequency-domain plot focuses on the peak value and ______.
A frequency-domain plot focuses on the peak value and ______.
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Frequency is formally expressed in ______ (Hz), which is cycle per second.
Frequency is formally expressed in ______ (Hz), which is cycle per second.
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In the example, the frequency of the sine wave is ______ Hz.
In the example, the frequency of the sine wave is ______ Hz.
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A signal with a frequency of 12 Hz has a period of ______.
A signal with a frequency of 12 Hz has a period of ______.
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The power we use at home has a frequency of ______ Hz.
The power we use at home has a frequency of ______ Hz.
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A frequency-domain plot does not show changes of amplitude during one ______.
A frequency-domain plot does not show changes of amplitude during one ______.
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Milliseconds are equivalent to ______ seconds.
Milliseconds are equivalent to ______ seconds.
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The peak value in the time domain sine wave is ______ V.
The peak value in the time domain sine wave is ______ V.
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A frequency of 1 kHz is equivalent to ______ Hz.
A frequency of 1 kHz is equivalent to ______ Hz.
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1 MHz is equivalent to ______ Hz.
1 MHz is equivalent to ______ Hz.
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The equivalent of 1 THz in Hertz is ______.
The equivalent of 1 THz in Hertz is ______.
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Each signal level is represented by ______ bits.
Each signal level is represented by ______ bits.
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The bit rate is the number of bits sent in ______.
The bit rate is the number of bits sent in ______.
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A page is an average of ______ lines with 80 characters in each line.
A page is an average of ______ lines with 80 characters in each line.
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A wire carrying electric signals gets ______ after a while.
A wire carrying electric signals gets ______ after a while.
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The required bit rate for downloading text documents at the rate of 100 pages per second is ______ bps.
The required bit rate for downloading text documents at the rate of 100 pages per second is ______ bps.
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To compensate for heat loss, ______ are used to amplify the signal.
To compensate for heat loss, ______ are used to amplify the signal.
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A digitized voice channel requires a bit rate of ______ bps.
A digitized voice channel requires a bit rate of ______ bps.
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For high-definition TV, the bit rate is approximately ______ Gbps.
For high-definition TV, the bit rate is approximately ______ Gbps.
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The unit used to measure the relative strengths of signals is the ______.
The unit used to measure the relative strengths of signals is the ______.
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TV stations typically reduce the bit rate to ______ to ______ Mbps through compression.
TV stations typically reduce the bit rate to ______ to ______ Mbps through compression.
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A decibel is negative if a signal is ______.
A decibel is negative if a signal is ______.
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The formula for calculating decibels in terms of power is dB = 10 log10 (P2/P1) where P2 and P1 are ______.
The formula for calculating decibels in terms of power is dB = 10 log10 (P2/P1) where P2 and P1 are ______.
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The concept of ______ is similar to wavelength for a digital signal, defining how far one bit occupies on the transmission medium.
The concept of ______ is similar to wavelength for a digital signal, defining how far one bit occupies on the transmission medium.
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If a signal's power is reduced to one-half, the attenuation can be calculated as ______ dB.
If a signal's power is reduced to one-half, the attenuation can be calculated as ______ dB.
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When a signal travels through an amplifier, its power can be increased ______ times.
When a signal travels through an amplifier, its power can be increased ______ times.
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The volume of the pipe defines the ______-delay product.
The volume of the pipe defines the ______-delay product.
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Power is proportional to the square of the ______.
Power is proportional to the square of the ______.
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Jitter is a problem if different packets encounter different ______.
Jitter is a problem if different packets encounter different ______.
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If the delay for the first packet is 20 ms and for the second is 45 ms, the application endures ______.
If the delay for the first packet is 20 ms and for the second is 45 ms, the application endures ______.
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The ______ of the pipe is related to its cross section and length.
The ______ of the pipe is related to its cross section and length.
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______ is an essential aspect to consider when dealing with real-time applications.
______ is an essential aspect to consider when dealing with real-time applications.
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The loss in the cable in decibels is 5 × (−0.3) = ______ dB.
The loss in the cable in decibels is 5 × (−0.3) = ______ dB.
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Distortion means that the signal changes its ______ or shape.
Distortion means that the signal changes its ______ or shape.
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Differences in delay may create a difference in ______ if the delay is not the same as the period duration.
Differences in delay may create a difference in ______ if the delay is not the same as the period duration.
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Noise is another cause of ______.
Noise is another cause of ______.
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Thermal noise is the random motion of ______ in a wire.
Thermal noise is the random motion of ______ in a wire.
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Induced noise comes from sources such as motors and ______.
Induced noise comes from sources such as motors and ______.
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Crosstalk is the effect of one wire on the ______.
Crosstalk is the effect of one wire on the ______.
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Impulse noise is a spike that comes from power lines, lightning, and ______.
Impulse noise is a spike that comes from power lines, lightning, and ______.
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Study Notes
Introduction to Physical Layer
- The physical layer moves data as electromagnetic signals across a transmission medium.
- Data is typically not in a format suitable for transmission, so it must be converted to signals.
- Signals can be analog (continuous) or digital (discrete).
- Only periodic analog signals can be used in data communication.
- Simple signals and composite signals are specific types of analog signals.
- Only nonperiodic digital signals are used in data communication.
- Digital signals have characteristics like bit rate and bit length.
- Transmission media, such as coaxial cable, fiber optic cable, or wireless, conduct signals along a physical path.
- Attenuation, distortion, and noise are transmission impairments that affect data signals.
- Data rate limit depends on factors like channel bandwidth and noise level.
Data and Signals
- Data can be analog or digital, corresponding to continuous or discrete states respectively.
- Analog signals have infinitely many levels of intensity; digital signals have a limited number of defined values (typically 0 or 1).
- Visual representations of analog and digital signals use graphs with vertical axes for values/strength and horizontal axes for time.
Periodic and Nonperiodic Signals
- Analog signals can be classified as periodic (repeating) or nonperiodic (no repeating pattern).
- A sine wave is a simple, periodic analog signal.
- Sine waves are characterized by peak amplitude, frequency, and phase.
- A composite analog signal consists of multiple sine waves.
Sine Wave
- The sine wave is the fundamental form of a periodic analog signal.
- It's visualized as a smooth, continuous, oscillating curve, changing over a cycle.
- Peak amplitude, frequency, and phase define a full sine wave cycle.
Peak Amplitude
- Peak amplitude is the highest intensity a signal reaches, representing energy carried by that signal.
- For electrical signals, it's usually measured in volts.
- Bigger amplitude means more energy.
Period and Frequency
- Period is time to complete one cycle.
- Frequency measures cycles per second (Hertz, Hz).
- Period and frequency are reciprocal.
- The formulas relating period and frequency are : T (period) = 1/f (frequency), and f = 1 / T
Phase
- Phase describes the position of a waveform relative to time zero.
- Phase shift is an offset or delay in the waveform's position.
- Phase is measured in degrees or radians.
Wavelength
- Wavelength is the distance a signal travels during one complete cycle.
- It depends on the propagation speed and frequency of the signal.
- Wavelength, propagation speed, and frequency are related mathematically.
Time and Frequency Domains
- Time-domain plots show changes in signal amplitude over time.
- Frequency-domain plots show the frequencies of components in a signal, with amplitude as a function of frequency.
- A sine wave represented by one spike in frequency-domain.
Composite Signals
- Signals consisting of multiple sine waves are called composite signals.
- Fourier analysis decomposes composite signals into constituent sine waves.
- Each component sine wave has its own frequency, amplitude, and phase.
- This method is used to understand periodic signals.
Bandwidth
- Bandwidth refers to a range of frequencies contained in a composite signal.
- It's calculated by subtracting the lowest from the highest frequency component.
- Infinite bandwidth signals are ideal signals. A channel's bandwidth is its capacity to transmit signals at certain frequencies.
Digital Signals / Bit Rate
- Digital signals use discrete voltage levels to represent data.
- Bit rate expresses the number of bits transmitted per second (bps);
- Bit rate depends on the signal level and bandwidth. Higher levels allow for faster bit rates if bandwidth is sufficient. There is a theoretical limit.
Noiseless Channel: Nyquist Bit Rate
- The Nyquist bit rate formula describes the maximum theoretical achievable bit rate in a noiseless channel.
- It's calculated by two times the bandwidth of the channel and logarithmic base 2 values of the number of signal levels to be used.
Noisy Channel: Shannon Capacity
- The Shannon capacity formula defines the maximum theoretical bit rate achievable in a noisy channel, taking into account signal-to-noise ratio (SNR).
- This calculation is more sophisticated than Nyquist and includes noise interference.
Transmission Impairment
- Attenuation: Loss of signal strength over distance.
- Distortion: Distortion of signal form during transmission.
- Noise: Extra signals added to the desired signal.
- Signal impairments reduce the fidelity of the received signals
Bandwidth-Delay Product
- Bandwidth-delay product is the number of bits that can fill a link at any instant of time.
- It's crucial for calculating the number of bits that can be in transit on a link.
- A high bandwidth-delay product signifies a higher potential data transfer capacity.
Jitter
- Jitter is variability in the delay of data packets.
- Jitter impairs applications requiring predictable data transmission timing
Throughput
- Throughput is the actual data rate achieved, unlike bandwidth which is the maximum theoretical data rate.
- It's affected by parameters like queuing time and processing delay.
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Description
Test your knowledge on the properties of waves and signals, including factors such as wavelength, frequency, and amplitude. This quiz covers key concepts essential for understanding wave behavior in various mediums. Perfect for students studying physics or engineering.
