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Communication Systems LA Solutions
- Q15.26(i): (i) The intensity of a light pulse travelling along a communication channel decreases exponentially with distance $x$ according to the relation $I = I_o e^{-\alpha x}$, where $I_o$ is the intensity at $x = 0$ and $\alpha$ is the attenuation constant. Show that the intensity reduces by 75 per cent after a distance of $\frac{\ln 4}{\alpha}$
- Q15.26(i): (i) The intensity of a light pulse travelling along a communication channel decreases exponentially with distance x according to the relation (I = I_{o}e^{-\alpha x}), where (I_{o}) is the intensity at (x = 0) and (\alpha) is the attenuation constant. Show that the intensity reduces by 75 per cent after a distance of (\frac{\ln 4}{\alpha})
- Q15.26(ii): (ii) Attenuation of a signal can be expressed in decibel (dB) according to the relation $\text{dB} = 10 \log_{10} \frac{I_o}{I}$. What is the attenuation in dB/km for an optical fibre in which the intensity falls by 50 per cent over a distance of 50 km?
- Q15.26(ii): (ii) Attenuation of a signal can be expressed in decibel (dB) according to the relation (\text{dB} =10 \log_{10}(\frac{I}{I_{o}})). What is the attenuation in dB/km for an optical fibre in which the intensity falls by 50 per cent over a distance of 50 km?
- Q15.27: A 50 MHz sky wave takes 4.04 ms to reach a receiver via re-transmission from a satellite 600 km above earth’s surface. Assuming re-transmission time by satellite negligible, find the distance between source and receiver. If communication between the two was to be done by Line of Sight (LOS) method, what should size and placement of receiving and transmitting antenna be?
- Q15.27: A 50 MHz sky wave takes 4.04 ms to reach a receiver via re-transmission from a satellite 600 km above earth’s surface. Assuming re-transmission time by satellite negligible, find the distance between source and receiver. If communication between the two was to be done by Line of Sight (LOS) method, what should size and placement of receiving and transmitting antenna be?
- Q15.28(i): An amplitude modulated wave is as shown in Fig. 15.4. Calculate (i) the percentage modulation,
- Q15.28(i): An amplitude modulated wave is as shown in Fig. 15.4. Calculate (i) the percentage modulation,
- Q15.28(ii): An amplitude modulated wave is as shown in Fig. 15.4. Calculate (ii) peak carrier voltage and,
- Q15.28(ii): An amplitude modulated wave is as shown in Fig. 15.4. Calculate (ii) peak carrier voltage and,
- Q15.28(iii): An amplitude modulated wave is as shown in Fig. 15.4. Calculate (iii) peak value of information voltage.
- Q15.28(iii): An amplitude modulated wave is as shown in Fig. 15.4. Calculate (iii) peak value of information voltage.
- Q15.29(i): (i) Draw the plot of amplitude versus ‘$\omega$’ for an amplitude modulated wave whose carrier wave ($\omega_c$) is carrying two modulating signals, $\omega_1$ and $\omega_2$ ($\omega_2 > \omega_1$).
- Q15.29(i): (i) Draw the plot of amplitude versus ‘(\omega)’ for an amplitude modulated wave whose carrier wave ((\omega_{c})) is carrying two modulating signals, (\omega_{1}) and (\omega_{2}) ((\omega_{2} > \omega_{1})). [Hint: Follow derivation from Eq 15.6 of NCERT Textbook of XII]
- Q15.29(ii): (ii) Is the plot symmetrical about $\omega_c$? Comment especially about plot in region $\omega < \omega_c$.
- Q15.29(ii): (ii) Is the plot symmetrical about (\omega_{c})? Comment especially about plot in region (\omega < \omega_{c}).
- Q15.29(iii): (iii) Extrapolate and predict the problems one can expect if more waves are to be modulated.
- Q15.29(iii): (iii) Extrapolate and predict the problems one can expect if more waves are to be modulated.
- Q15.29(iv): (iv) Suggest solutions to the above problem. In the process can one understand another advantage of modulation in terms of bandwidth?
- Q15.29(iv): (iv) Suggest solutions to the above problem. In the process can one understand another advantage of modulation in terms of bandwidth?
- Q15.30(i): An audio signal is modulated by a carrier wave of 20MHz such that the bandwidth required for modulation is 3kHz. Could this wave be demodulated by a diode detector which has the values of $R$ and $C$ as (i) $R = 1 \text{ k}\Omega$, $C = 0.01\mu\text{F}$.
- Q15.30(i): An audio signal is modulated by a carrier wave of 20MHz such that the bandwidth required for modulation is 3kHz. Could this wave be demodulated by a diode detector which has the values of (R) and (C) as (i) (R = 1 \text{ k}\Omega), (C = 0.01\mu\text{F}).
- Q15.30(ii): An audio signal is modulated by a carrier wave of 20MHz such that the bandwidth required for modulation is 3kHz. Could this wave be demodulated by a diode detector which has the values of $R$ and $C$ as (ii) $R = 10 \text{ k}\Omega$, $C = 0.01\mu\text{F}$.
- Q15.30(ii): An audio signal is modulated by a carrier wave of 20MHz such that the bandwidth required for modulation is 3kHz. Could this wave be demodulated by a diode detector which has the values of (R) and (C) as (ii) (R = 10 \text{ k}\Omega), (C = 0.01\mu\text{F}).
- Q15.30(iii): An audio signal is modulated by a carrier wave of 20MHz such that the bandwidth required for modulation is 3kHz. Could this wave be demodulated by a diode detector which has the values of $R$ and $C$ as (iii) $R = 10 \text{ k}\Omega$, $C = 0.1\mu\text{F}$.
- Q15.30(iii): An audio signal is modulated by a carrier wave of 20MHz such that the bandwidth required for modulation is 3kHz. Could this wave be demodulated by a diode detector which has the values of (R) and (C) as (iii) (R = 10 \text{ k}\Omega), (C = 0.1\mu\text{F}).
Other Exercises for CBSE - Class 12 Physics Communication Systems
Chapters in CBSE - Class 12 Physics
- Electric Charges and Fields
- Electrostatic Potential and Capacitance
- Current Electricity
- Moving Charges and Magnetism
- Magnetism and Matter
- Electromagnetic Induction
- Alternating Current
- Electromagnetic Waves
- Ray Optics and Optical Instruments
- Wave Optics
- Dual Nature of Radiation and Matter
- Atoms
- Nuclei
- Semiconductor Electronics
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