Bihar School Examination Board

Physics Chapter Test

Communication Systems

Time: 1 Hour 30 Minutes

Class: XII

Maximum Marks: 35

General Instructions:

• All questions are compulsory.
• There are three sections: Section A (MCQs), Section B (Short Answer), and Section C (Long Answer).
• Section A contains 10 questions of 1 mark each.
• Section B contains 5 questions of 2 marks each.
• Section C contains 3 questions of 5 marks each.
• Use diagrams wherever necessary to support your answers.
• Attempt all questions in sequence.

Section A: Multiple Choice Questions (1 mark each)

Question 1

1 mark

The process of superimposing a low-frequency signal on a high-frequency wave is known as:

A

Attenuation

B

Modulation

C

Demodulation

D

Transmission

Question 2

1 mark

The frequency range for satellite communication is:

A

1-10 MHz

B

30-300 MHz

C

1-10 GHz

D

100-1000 GHz

Question 3

1 mark

Which of the following is NOT an essential component of a communication system?

A

Transmitter

B

Receiver

C

Channel

D

Oscillator

Question 4

1 mark

The phenomenon by which the height of the ionosphere varies with time is called:

A

Refraction

B

Reflection

C

Fading

D

Skip distance

Question 5

1 mark

In amplitude modulation, the bandwidth is equal to:

A

ω_m

B

2ω_m

C

ω_c

D

2ω_c

Section B: Short Answer Questions (2 marks each)

Question 6

2 marks

Explain the term 'modulation index' in amplitude modulation. What happens when the modulation index is greater than 1?

Write your answer here...

Question 7

2 marks

Differentiate between ground wave propagation and space wave propagation of electromagnetic waves.

Write your answer here...

Question 8

2 marks

What is the function of a repeater in communication systems? Explain with a diagram.

Write your answer here (include diagram if needed)...

Question 9

2 marks

Why is the transmission of signals using baseband not suitable for long distances?

Write your answer here...

Section C: Long Answer Questions (5 marks each)

Question 10

5 marks

With the help of a block diagram, explain the functioning of the transmitter in a communication system. Describe the role of each component.

Write your detailed answer here (include diagram if needed)...

Question 11

5 marks

What is amplitude modulation? Derive the expression for an amplitude modulated wave. Draw the frequency spectrum of AM wave.

Write your detailed answer here (include derivation and diagram)...

Question 12

5 marks

Explain sky wave propagation with special reference to critical frequency and skip distance. Why is this mode of propagation suitable for short-wave broadcast services?

Write your detailed answer here...

You've reached the end of the test. Please review your answers before submission.

Bihar School Examination Board - Physics Test

Chapter: Communication Systems

Physics Textbook Reference

Class XII Curriculum

www.biharboardonline.bihar.gov.in