Important Questions for Class 12 Chapter 15 - Communication Systems

Important questions based on NCERT syllabus for Chapter 15 - Communication Systems:

Question-1: Digital signals
(i) do not provide a continuous set of values,
(ii) represent values as discrete steps,
(iii) can utilize binary system, and
(iv) can utilize decimal as well as binary systems.
Which of the above statements are true?
(a) (i) and (ii) only
(b) (ii) and (iii) only
(c) (i), (ii) and (iii) but not (iv)
(d) All of (i), (ii), (iii) and (iv).

Solution: (c)

Question-2: Is it necessary for a transmitting antenna to be at the same height as that of the receiving antenna for line-of-sight communication? A TV transmitting antenna is 81m tall. How much service area can it cover if the receiving antenna is at the ground level?

Solution:
No, it is not necessary.
Service Area Covered = d2 = 3.14 x 162 x 6.4 x 106 = 3258 sq km.

Question-3: Which of the following frequencies will be suitable for beyond-the horizon communication using sky waves?
(a) 10 kHz
(b) 10 MHz
(c) 1 GHz
(d) 1000 GHz

Solution: (b)