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CBSE - Class 12 Physics Communication Systems Worksheet

1.
(ii) Is the plot symmetrical about $\omega_c$? Comment especially about plot in region $\omega < \omega_c$.
2.

I can smell the flowers in the garden, see a hummingbird flitting through the air, and hear leaves rustling in the light breeze.

a.

NO CHANGE

 b.

I'm seeing

 c.

I can even see

 d.

while seeing
3.

Carl appears to be smarter ______ his brother.

a.

then

 b.

than
4.
A male voice after modulation-transmission sounds like that of a female to the receiver. The problem is due to
a. poor selection of modulation index (selected $0 < m < 1$) b. poor bandwidth selection of amplifiers. c. poor selection of carrier frequency d. loss of energy in transmission.
5.
(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?
6.

Which of the following sentences is punctuated correctly.

a.





Is that your mother’s car? - No it’s my sisters.
 b.

Is that your mothers’ car? - No it’s my sisters.

 c.

Is that your mother’s car? - No it’s my sister’s.

 d.





Is that your mothers car? - No it’s my sisters’.
7.
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?
8.

Which of the following sentences is punctuated correctly.

a.

The project will take about a years' work.

 b.

The project will take about a year's work.

 c.

The project will take about a years work.
9.

However, roadies must also be competent mechanics for their band, inspecting, repair, and maintaining the equipment.

a.

NO CHANGE

 b.

roadies repairing

 c.

to repair

 d.

repairing
10.

Influenced by media portrayals like the television dog Lassie, people perceive dogs as friendly and cats are vilified.

a.

NO CHANGE

 b.

cats as being vilified

 c.

cats as vilainous

 d.

vilified cats
11.

Environmentalists make many arguments against fracking: it contaminates drinking water supplies, creates greenhouse gas emissions, and it lowers air quality in the surrounding area.

a.

NO CHANGE

 b.

lowering

 c.

lowers

 d.

will lower
12.
A basic communication system consists of
(A) transmitter.
(B) information source.
(C) user of information.
(D) channel.
(E) receiver.
Choose the correct sequence in which these are arranged in a basic communication system:
a. ABCDE. b. BADEC. c. BDACE. d. BEADC.
13.
(iv) Suggest solutions to the above problem. In the process can one understand another advantage of modulation in terms of bandwidth?
14.
Identify the mathematical expression for amplitude modulated wave:
a. $A_c \sin [\{\omega_c + k_1 v_m(t)\}t + \phi]$. b. $A_c \sin \{\omega_c t + \phi + k_2 v_m(t)\}$. c. $\{A_c + k_2 v_m(t)\} \sin (\omega_c t + \phi)$. d. $A_c v_m(t) \sin (\omega_c t + \phi)$.
15.

Which of the following sentences is punctuated correctly.

a.





Is that your mother’s car? - No it’s my sisters.
 b.

Is that your mothers’ car? - No it’s my sisters.

 c.

Is that your mother’s car? - No it’s my sister’s.

 d.





Is that your mothers car? - No it’s my sisters’.
16.

I've been looking for my keys _______ the last 10 minutes. can you help me?

a.

For

 b.

Since
17.

Many bizarre, unique treasure chests containing small novelties and useless trinkets have been hidden over the last few years, some within cities but several others on tall mountains, in narrow covers, or left in wilderness like wastelands or swamps.

a.

NO CHANGE

 b.

they were left in

 c.

in

 d.

DELETE the left in word
18.

Randolph ________ my invitation to dinner.

a.

accepted

 b.

expected
19.

I will try not to let his words ________ me.

a.

affect

 b.

effect
20.
A 100m long antenna is mounted on a 500m tall building. The complex can become a transmission tower for waves with $\lambda$
a. ~ 400 m. b. ~ 25 m. c. ~ 150 m. d. ~ 2400 m.

Worksheet Answers

2.
Option D
3.
Option B
4.
6.
Option C
8.
Option B
9.
Option C
10.
Option C
11.
Option D
12.
14.
15.
Option C
16.
Option A
17.
Option D
18.
Option A
19.
Option B
20.
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