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MCQOPTIONS
This section includes 12583 Mcqs, each offering curated multiple-choice questions to sharpen your Joint Entrance Exam - Main (JEE Main) knowledge and support exam preparation. Choose a topic below to get started.
| 2951. |
What is the band width in amplitude modulation? |
| A. | Equal to signal frequency |
| B. | Two times the signal frequency |
| C. | Half the signal frequency |
| D. | One fourth the signal frequency |
| Answer» C. Half the signal frequency | |
| 2952. |
In frequency modulated wave: |
| A. | frequency varies with time |
| B. | amplitude varies with time |
| C. | both frequency and amplitude vary with time |
| D. | both frequency and amplitude are constant |
| Answer» B. amplitude varies with time | |
| 2953. |
In light modulation, which characteristic of the carrier light wave is varied? |
| A. | Amplitude |
| B. | Frequency |
| C. | Phase |
| D. | Intensity |
| Answer» B. Frequency | |
| 2954. |
An AM- signal is given as \[{{x}_{AM}}(t)=100\,[p(t)+0.5\,g(t)]\,\,\cos \,{{\omega }_{c}}t\] in interval \[0\le t\le 1.\]. One set of possible values of the modulating signal and modulation index would be |
| A. | \[t,\,\,0.5\] |
| B. | \[t,\,\,1.0\] |
| C. | \[t,\,\,1.5\] |
| D. | \[{{t}^{2}},\,\,2.0\] |
| Answer» B. \[t,\,\,1.0\] | |
| 2955. |
An FM signal has a resting frequency of \[105\text{ }MHz\] and highest frequency of \[105.03\text{ }MHz\] when modulated by a signal of frequency \[5\text{ }kHz.\]The carrier swing is |
| A. | \[25\,kHz\] |
| B. | \[54\,kHz\] |
| C. | \[60\,kHz\] |
| D. | \[75\,kHz\] |
| Answer» D. \[75\,kHz\] | |
| 2956. |
A detector circuit must - |
| A. | rectify the signal |
| B. | deliver an audio output signal |
| C. | perform the above two functions |
| D. | None of the above |
| Answer» D. None of the above | |
| 2957. |
In an FM system a \[7\text{ }kHz\] signal modulates \[108\,MHz\]carrier so that frequency deviation is\[50\,kHz\]. The carrier swing is |
| A. | \[7.1\] |
| B. | \[2.8\] |
| C. | \[5.8\] |
| D. | \[3.2\] |
| Answer» B. \[2.8\] | |
| 2958. |
A laser beam is used for carrying out surgery because it |
| A. | is highly monochromatic |
| B. | is highly coherent |
| C. | is highly directional |
| D. | can be sharply focused |
| Answer» E. | |
| 2959. |
At maximum modulation (i.e. \[m=1\]), the power in each sideband is......... of that of carrier. |
| A. | \[25%\] |
| B. | \[50%\] |
| C. | \[40%\] |
| D. | \[60%\] |
| Answer» B. \[50%\] | |
| 2960. |
For good demodulation of AM signal of carrier frequency/, the value of RC should be |
| A. | \[RC=\frac{1}{f}\] |
| B. | \[RC<\frac{1}{f}\] |
| C. | \[RC\ge \frac{1}{f}\] |
| D. | \[RC>>\frac{1}{f}\] |
| Answer» E. | |
| 2961. |
The maximum distance upto which TV transmission from a TV tower of height h can be received is proportional to - |
| A. | \[{{h}^{1/2}}\] |
| B. | h |
| C. | \[{{h}^{3/2}}\] |
| D. | \[{{h}^{2}}\] |
| Answer» B. h | |
| 2962. |
A \[1000\text{ }kHz\] carrier is simultaneously modulated with \[300\text{ }Hz,\] \[800\text{ }Hz\] and \[2\text{ }kHz\] audio waves. The frequencies present in the output is |
| A. | \[999.7\text{ }kHz,\text{ }100.3\text{ }kHz,\text{ }999.2\text{ }kHz\] |
| B. | \[1000.8\text{ }kHz,\text{ }998\text{ }kHz,\text{ }1002\text{ }kHz\] |
| C. | \[1002.8\text{ }kHz,\text{ }996\text{ }kHz,\text{ }1106\text{ }kHz\] |
| D. | both (a) and (b) |
| Answer» E. | |
| 2963. |
A sinusoidal carrier voltage of frequency \[10\text{ }MHz\] and amplitude 200 volts is amplitude modulated by a sinusoidal voltage of frequency \[10\text{ }kHz\]producing \[40%\]modulation. Calculate the frequency of upper and lower sidebands. |
| A. | \[10010kHz,9990\text{ }kHz\] |
| B. | \[1010kHz,990kHz\] |
| C. | \[10100\text{ }Hz,9990\text{ }Hz\] |
| D. | \[1010MHz,990MHz\] |
| Answer» B. \[1010kHz,990kHz\] | |
| 2964. |
The wrong statement is |
| A. | Electromagnetic waves with frequencies more than the critical frequency of ionosphere cannot be used for communication using sky wave propagation. |
| B. | The refractive index of the ionosphere becomes very high for frequencies higher than the critical frequency. |
| C. | Diode lasers are used as optical sources in optical communication. |
| D. | Diode lasers consume more energy. |
| Answer» E. | |
| 2965. |
A carrier frequency of \[1\text{ }MHz\] and peak value of \[10\text{ }V\] is amplitude modulated with a signal frequency of \[10\text{ }kHz\] with peak value of\[0.5\text{ }V\]. Then, the modulation index and the side band frequencies respectively are |
| A. | \[0.05\]and\[1\pm 0.010\text{ }MHz\] |
| B. | \[0.5\]and \[1\pm 0.010\text{ }MHz\] |
| C. | \[0.5\]and \[1\pm 0.005\text{ }MHz\] |
| D. | \[0.05\]and \[1\pm 0.005\text{ }MHz\] |
| Answer» B. \[0.5\]and \[1\pm 0.010\text{ }MHz\] | |
| 2966. |
The rms value of a carrier voltage is 100 volts. Compute its rms value when it has been amplitude modulated by a sinusoidal audio voltage to a depth of 30%. |
| A. | \[94\,V\] |
| B. | \[104.5\,V\] |
| C. | \[114.4\,V\] |
| D. | \[124\,V\] |
| Answer» C. \[114.4\,V\] | |
| 2967. |
The maximum peak to peak voltage of an AM wire is \[24\text{ }mV\] and the minimum peak to peak voltage is \[8\text{ }mV\]. The modulation factor in percentage is |
| A. | \[10%\] |
| B. | \[20%\] |
| C. | \[25%\] |
| D. | \[50%\] |
| Answer» E. | |
| 2968. |
The antenna current of an AM transmitter is 8 A when only the carrier is sent, but it increases to 893 A when the carrier is sent, but it increases to 893 A when the carrier is modulated by a single sine wave. Find the percentage modulation. |
| A. | \[60.1%\] |
| B. | \[70.1%\] |
| C. | \[80.1%\] |
| D. | \[50.1%\] |
| Answer» C. \[80.1%\] | |
| 2969. |
100% modulation in FM means , |
| A. | actual frequency deviation > maximum allowed frequency deviation |
| B. | actual frequency deviation = maximum allowed frequency deviation |
| C. | actual frequency deviation > maximum allowed frequency deviation |
| D. | actual frequency deviation < maximum allowed frequency deviation |
| Answer» C. actual frequency deviation > maximum allowed frequency deviation | |
| 2970. |
The electromagnetic waves of frequency \[2\text{ }MHz\] to \[30\text{ }MHz\] are used |
| A. | in ground wave propagation |
| B. | in sky wave propagation |
| C. | in microwave propagation |
| D. | in satellite communication |
| Answer» C. in microwave propagation | |
| 2971. |
A signal of peak voltage \[5\text{ }V\] at \[10\text{ }kHz\] is modulated using a carrier wave of peak voltage \[10\text{ }V\] at\[2\text{ }MHz\]. The side band frequencies are |
| A. | \[2010kHz,1990kHz\] |
| B. | \[2000kHz,\text{ }1990kHz\] |
| C. | \[2010kHz,\text{ }2000\text{ }kHz\] |
| D. | \[2100kHz,\text{ }1900kHz\] |
| Answer» B. \[2000kHz,\text{ }1990kHz\] | |
| 2972. |
For television broadcasting, the frequency employed is normally - |
| A. | \[30-300\text{ }MHz\] |
| B. | \[3-30\text{ }MHz\] |
| C. | \[30-300\text{ }KHz\] |
| D. | \[30-300\text{ }Hz\] |
| Answer» B. \[3-30\text{ }MHz\] | |
| 2973. |
If the heights of transmitting and the receiving antennas are each equal to h, the maximum line- of-sight distance between them is (R is the radius of earth) |
| A. | \[\sqrt{2Rh}\] |
| B. | \[\sqrt{4Rh}\] |
| C. | \[\sqrt{6Rh}\] |
| D. | \[\sqrt{8Rh}\] |
| Answer» E. | |
| 2974. |
A super heterodyne receiver is designed to receive transmitted signals between 5 and\[10\text{ }MHz\]. The tuning range of the local oscillate for IF frequency \[600\text{ }kHz\] for high-side tuning would be |
| A. | \[4.6\] to\[9.6\text{ }MHz\] |
| B. | \[5.6\] to \[10.6\text{ }MHz\] |
| C. | \[4.6\] to\[10.6\text{ }MHz\] |
| D. | \[5.6\] to \[9.6\text{ }MHz\] |
| Answer» C. \[4.6\] to\[10.6\text{ }MHz\] | |
| 2975. |
Range of frequencies allotted for commercial FM radio broadcast is - |
| A. | \[88\]to\[108\text{ }MHz\] |
| B. | \[88\] to \[108\text{ }kHz\] |
| C. | \[8\]to\[88\text{ }MHz\] |
| D. | \[88\] to \[108\text{ }GHz\] |
| Answer» B. \[88\] to \[108\text{ }kHz\] | |
| 2976. |
Modulation is the process of superposing |
| A. | low frequency audio signal on high frequency waves |
| B. | low frequency radio signal on low frequency audio waves |
| C. | high frequency audio signal on low frequency radio waves |
| D. | low frequency audio signal on low frequency radio waves |
| Answer» B. low frequency radio signal on low frequency audio waves | |
| 2977. |
In a radio receiver, noise is generally developed at- |
| A. | IF stage |
| B. | audio stage |
| C. | RF stage |
| D. | receiving antenna |
| Answer» D. receiving antenna | |
| 2978. |
A TV tower has a height of\[100m\]. By how much the height of tower be increased to triple its coverage range? |
| A. | \[800\text{ }m\] |
| B. | \[700\text{ }m\] |
| C. | \[600\text{ }m\] |
| D. | \[500\text{ }m\] |
| Answer» B. \[700\text{ }m\] | |
| 2979. |
Which one of the following is used in line-transmission - |
| A. | coaxial cable |
| B. | optical fibre cable |
| C. | twisted pair |
| D. | all the above |
| Answer» E. | |
| 2980. |
What should be the maximum acceptance angle at the aircore interface of an optical fibre if \[{{n}_{1}}\]and \[{{n}_{2}}\] are the refractive indices of the core and the cladding, respectively? |
| A. | \[{{\sin }^{-1}}({{n}_{2}}/{{n}_{1}})\] |
| B. | \[{{\sin }^{-1}}\sqrt{n_{1}^{2}-n_{2}^{2}}\] |
| C. | \[\left[ {{\tan }^{-1}}\frac{{{n}_{2}}}{{{n}_{1}}} \right]\] |
| D. | \[\left[ {{\tan }^{-1}}\frac{{{n}_{1}}}{{{n}_{2}}} \right]\] |
| Answer» C. \[\left[ {{\tan }^{-1}}\frac{{{n}_{2}}}{{{n}_{1}}} \right]\] | |
| 2981. |
The electron density of a layer of ionosphere at a height \[150\text{ }km\] from the earth's surface is \[9\times {{10}^{9}}\,per\,{{m}^{3}}.\]For the sky transmission from this layer up to a range of \[250\text{ }km,\]The critical frequency of the layer is |
| A. | \[2\,Hz\] |
| B. | \[2.7\,Hz\] |
| C. | \[2.78\,Hz\] |
| D. | \[2.7\,MHz\] |
| Answer» E. | |
| 2982. |
Communication satellite is used when the distance of transmission is greater than - |
| A. | \[100\,km\] |
| B. | \[500\,km\] |
| C. | \[10\,km\] |
| D. | \[1000\,km\] |
| Answer» E. | |
| 2983. |
In an optical fibre, the diameter of the core is nearly |
| A. | \[{{10}^{-2}}m\] |
| B. | \[{{10}^{-4}}m\] |
| C. | \[{{10}^{-8}}m\] |
| D. | \[{{10}^{-10}}m\] |
| Answer» C. \[{{10}^{-8}}m\] | |
| 2984. |
In which frequency range, space waves are normally propagated |
| A. | HF |
| B. | VHF |
| C. | UHF |
| D. | SHF |
| Answer» D. SHF | |
| 2985. |
A transducer used at the transmitting end, serves the purpose of converting |
| A. | electrical signal to sound form |
| B. | sound signal to electrical form |
| C. | electrical signal to magnetic form |
| D. | sound signal to magnetic form |
| Answer» C. electrical signal to magnetic form | |
| 2986. |
In ground or surface wave propagation, the loss of power in a signal wave is due to |
| A. | induced charges in earth which travel in ground along with the wave, resulting the alternating currents in the earth's surface |
| B. | interference of waves |
| C. | superposition of waves |
| D. | high frequency of signal wave. |
| Answer» B. interference of waves | |
| 2987. |
In earth's atmosphere, for \[{{F}_{2}}\] -layer, the virtual height and critical frequency in night time are |
| A. | \[210\,km\] and \[5\text{ }MHz\] |
| B. | \[250\,km\] and \[6\,MHz\] |
| C. | \[280\text{ }km\] and \[7\text{ }MHz\] |
| D. | \[350\,km\] and \[6\,MHz\] |
| Answer» E. | |
| 2988. |
In an amplitude modulated wave for audio frequency of 500 cycle/second, the appropriate carrier frquency will be |
| A. | \[50\,cycles/s\] |
| B. | \[100\,cycles/s\] |
| C. | \[500\,cycles/s\] |
| D. | \[50,000\,cycles/s\] |
| Answer» E. | |
| 2989. |
Electromagnetic waves with frequencies greater than the critical frequency of ionosphere cannot be used for communication using sky wave propagation because: |
| A. | the refractive index of the ionosphere becomes very high for \[f>{{f}_{c}}\] |
| B. | the refractive index of the ionosphere becomes very low for \[f>{{f}_{c}}\] |
| C. | the refractive index of the ionosphere very high for \[f<{{f}_{c}}\] |
| D. | none of the above |
| Answer» B. the refractive index of the ionosphere becomes very low for \[f>{{f}_{c}}\] | |
| 2990. |
The radio waves of frequency \[300\text{ }MHz\] to \[3000\text{ }MHz\] belong to |
| A. | high frequency band |
| B. | very high frequency band |
| C. | ultra high frequency band |
| D. | super high frequency band |
| Answer» D. super high frequency band | |
| 2991. |
The TV telecast is to cover a radius of \[120\text{ }km\] (given the radius of the Earth\[=6400\text{ }km\]), the height of the transmitting antenna is |
| A. | \[1280\,m\] |
| B. | \[1125\,m\] |
| C. | \[1560\,m\] |
| D. | \[79\text{ }m\] |
| Answer» C. \[1560\,m\] | |
| 2992. |
Audio signal cannot be transmitted because |
| A. | the signal has more noise f Thinking |
| B. | the signal cannot be amplified for distance communication |
| C. | the transmitting antenna length is very small to design |
| D. | the transmitting antenna length is very large and impracticable |
| Answer» C. the transmitting antenna length is very small to design | |
| 2993. |
The fundamental radio antenna is a metal rod which has a length equal to |
| A. | \[\lambda \] in free space at the frequency of operation |
| B. | \[\lambda /2\] in free space at the frequency of operation |
| C. | \[\lambda /4\] in free space at the frequency of operation |
| D. | \[3\lambda /4\] in free space at the frequency of operation |
| Answer» D. \[3\lambda /4\] in free space at the frequency of operation | |
| 2994. |
The attenuation in optical fibre is mainly due to |
| A. | absorption |
| B. | scattering |
| C. | neither absorption nor scattering |
| D. | both (a) and (b) |
| Answer» E. | |
| 2995. |
The phenomenon by which light travels in an optical fibres is |
| A. | Reflection |
| B. | Refraction |
| C. | Total internal reflection |
| D. | Transmission |
| Answer» D. Transmission | |
| 2996. |
Critical frequency \[{{v}_{c}}\] for the ionosphere is - |
| A. | \[{{v}_{c}}=9.{{N}_{\max }}\] |
| B. | \[{{v}_{c}}=9\sqrt{{{N}_{\max }}}\] |
| C. | \[{{v}_{c}}=6.IN\max \] |
| D. | \[{{v}_{c}}=6.{{N}_{max}}\] |
| Answer» C. \[{{v}_{c}}=6.IN\max \] | |
| 2997. |
The temperature of earth's atmosphere increases with height in |
| A. | troposphere |
| B. | stratosphere and ionosphere |
| C. | mesosphere and tonosphere |
| D. | None of these |
| Answer» C. mesosphere and tonosphere | |
| 2998. |
What will be the image frequency of an FM radio receiver that is tuned to \[98.6\text{ }MHz\] broadcast station? |
| A. | \[111.8\,MHz\] |
| B. | \[108\,MHz\] |
| C. | \[121.6\,MHz\] |
| D. | \[132\,MHz\] |
| Answer» D. \[132\,MHz\] | |
| 2999. |
A T.V. tower has a height 150 m. What is the population density around the T.V. tower if the total population covered is 50 lakh? The radius of earth is \[6.4\times {{10}^{6}}m\]. |
| A. | \[800\,k{{m}^{-2}}\] |
| B. | \[829\,k{{m}^{-2}}\] |
| C. | \[82.6\,k{{m}^{-2}}\] |
| D. | \[826.6\,k{{m}^{-2}}\] |
| Answer» C. \[82.6\,k{{m}^{-2}}\] | |
| 3000. |
The maximum range for the tropospheric transmission of radio wave of wavelength 3m using the transmitting antenna and receiving antenna of heights \[100\,m\] and \[60\,m\] respectively is |
| A. | \[8\,m\] |
| B. | \[800\,m\] |
| C. | \[8\,km\] |
| D. | \[80\,km\] |
| Answer» D. \[80\,km\] | |