(i) (a) Concern
(b) Scientific temperament
(c) Keen observer
(d) Alertness
(ii) d= \(\sqrt { 2hR } \)
=  \(\sqrt { 2\times 20\times 6.4\times { 10 }^{ 6 } } \) m
= 2 x 8 x 10³ m
= 16 km

(a) In the process of modulation, some specific characteristics of the carrier wave is varied in accordance with the information or message signal.
The carrier wave may be :
(i) Continuous (sinusoidal) wave, or
(ii) Pulse, which is discontinuous.
A continuous sinusoidal carrier wave can be expressed as
\(E={ E }_{ 0 }sin\left( \omega t+\phi \right)\)
Three distinct characteristics of such a wave are amplitude (E₀ ), angular frequency \(\left( \omega \right) \)  and phase angle \(\left( \phi \right) \) . Anyone of these three characteristics can be varied in accordance with the modulating baseband (AF) signal, giving rise to the respective amplitude modulation; frequency modulation and phase modulation.
Again, the significant characteristics of a pulse are pulse amplitude, pulse duration or pulse width and pulse position (representing the time of rise or fall of the pulse amplitude). Anyone of these characteristics can be varied in accordance with the modulating baseband (AF)signal, giving rise to the respective, pulse amplitude modulation (PAM), pulse duration modulation (PDM) or pulse width modulation (PWM) and pulse position modulation (PPM).
(b) Amplitude Modulation: When a modulating AF wave is superimposed on a high frequency carrier wave in a manner that the frequency of modulated wave is same as that of the carrier wave, but its amplitude is made proportional to the instantaneous amplitude of the audio frequency modulating voltage, the process is called amplitude modulation (AM).
Let the instantaneous carrier voltage (e_c ) and modulating voltage (em) be represented by
\({ e }_{ c }={ E }_{ c }sin{ \omega }_{ c }t ...(i)\)
\(\\ { e }_{ m }={ E }_{ m }sin{ \omega }_{ m } \quad ...(ii)\)
Thus, in amplitude modulation, amplitude A of modulated wave is made proportional to the instantaneous modulating voltage e_m
\(i.e., A={ E }_{ c }+{ ke }_{ m }\quad ...(iii)\)
where k is a constant of proportionality.
In amplitude modulation, the proportionality constant k is made equal to unity. Therefore, maximum positive amplitude of AM wave is given by
\(A={ E }_{ c }+{ e }_{ m }={ E }_{ c }+{ E }_{ m }\)
\(sin \ { \omega }_{ m }t \ \ ...(iv)\)
It is called top envelope.
The maximum negative amplitude of AM wave is given by
\(-A=-{ E }_{ c }-{ e }_{ m }\)
\(=-\left( { E }_{ c }+{ E }_{ m }sin\ { \omega }_{ m }t \right) ...(v)\)

(a) The value shown by Samir are:
(i)  Curiosity
(ii) Creativity
(iii) Sharing Knowledge.
(b) Moon cannot be used as a communication satellite, because:
(i)   The surface of the Moon is so rough and uneven that most of the signal scatters back into space instead of bouncing back to the earth.
(ii)  The moon can only reflect signals while modern communication satellites actively rebroadcast the signal back to the earth.
(iii) The moon is only available for half of the day and it keeps moving.

(i) Electromagnetic radiations emitted by an antenna can cause
(a) Cardiac problem
(b) cancer
(c) Giddiness and headache
(any one of the above / or any other effect on health)
(ii) Scientific temperament, awareness (anyone / any other correct value)
(iii) \(Range \ = \ \sqrt { { 2h }_{ \tau }R }\)
\(= \ \sqrt { 2\times 20\times 6.4\times { 10 }^{ 6 } } \ km\)
\(= \ \sqrt { 4\times 64\times { 10 }^{ 6 } } = \ 16 \ km\)

(a) The values displayed by Rakhi are :
(i) High degree of general awareness.
(ii) The proper knowledge of subject matter.
(iii) Helping and caring nature.
(b) Given, V_m = 10 kHz, V_c = 1 MHz,
A_m = 10V and A_c = 20 V
(i) Thus, modulation index,
\(\mu =\frac { { A }_{ m } }{ { A }_{ c } } =\frac { 10 }{ 20 } =0.5\)
(ii) Frequencies of side bands
\(={ V }_{ c }\overset { + }{ - } { V }_{ m }\)
\(= 1MHz\overset { + }{ - } 10kHz\)
\(=990kHz\ and\ 1010kHz\) 

(a) The ultra-high frequency em radiations, continuously emitted by a mobile phone, may harm the system of the human body.
(b) Sister Anita shown
(i) Concern about her brother
(ii)  Awareness about the likely effects of em radiations on human body
(iii) Sense of responsibility   any two)
(c) The sidebands are
\(({ V }_{ c }+{ \upsilon }_{ m }) \ and \ ({ V }_{ c }-{ \upsilon }_{ m })\)
\(or \  (1000 \  + \  10) \  kHz \  and \  (1000 \  - \  10) \ kHz  \)
\(1010 \ kHz \ and \ 990 \ kHz\)

(i)  Radio wave communication system.
(ii)  Use of scientific and technological advancement in service to mankind.
(iii) Patriotism and love for the country, presence of mind.
(iv) Television communication system.

(i)   As set up that transfer information implicitly from one point to another is called communication system. Analog signal is better than a digital signal.
(ii) Sohan is an intelligent and knowledgeable person.
(iii) There are three communication satellites.
(iv) The three groups display the values if eagerness to engage in adebate, promptness in taking decision and ability to work in a constructive manner.

Here, v_m = 15000 Hz = 15 kHz
C = 1 nF = 10^-9 F, v_SB = ?
L = 10 \(\mu\) H = 10 x 10^-6 H = 10^-5 H
\({ v }_{ c }=\frac { 1 }{ 2\pi \sqrt { LC } } =\frac { 1 }{ 2\times \frac { 22 }{ 7 } \sqrt { { 10 }^{ -5 }\times { 10 }^{ -9 } } } \)
\(=\frac { { 10 }^{ 7 }\times 7 }{ 44 } Hz=1592kHz\)
\({ v }_{ SB }={ v }_{ c }\pm { v }_{ m }=1592\pm 15\)
\(=1607kHz \ or \ 1577 \ kHz\)

Here, l = 1?
v = 15 MHz = 15 x 10⁶ Hz
\(\lambda =\frac { c }{ v } =\frac { 3\times { 10 }^{ 8 } }{ 15\times { 10 }^{ 6 } } =20\ m\) 
Length of Marconi antenna,
\(l=\frac { \lambda }{ 4 } =\frac { 20 }{ 4 } =5\ m\)