NIOS Class 12 Physics Chapter 30 Communication Systems

NIOS Class 12 Physics Chapter 30 Communication Systems Solutions English Medium As Per New Syllabus to each chapter is provided in the list so that you can easily browse throughout different chapters NIOS Class 12 Physics Chapter 30 Communication Systems Notes in English and select need one. NIOS Class 12 Physics Solutions English Medium Download PDF. NIOS Study Material of Class 12 Physics Notes Paper Code: 312.

NIOS Class 12 Physics Chapter 30 Communication Systems

Also, you can read the NIOS book online in these sections Solutions by Expert Teachers as per National Institute of Open Schooling (NIOS) Book guidelines. These solutions are part of NIOS All Subject Solutions. Here we have given NIOS Class 12 Physics Notes, NIOS Senior Secondary Course Physics Solutions in English for All Chapter, You can practice these here.

Communication Systems

Chapter: 30

Module-VIII: Semiconductor Devices And Communication

INTEXT QUESTIONS 30.1

1. What is an electromagnetic wave?

Ans: An electromagnetic (EM) wave is a self-propagating disturbance in which a time-varying electric field produces a time-varying magnetic field, and vice-versa, so the two fields sustain each other and travel together through space at the speed of light (3 × 10⁸ m s⁻¹).

(i) The electric field E and magnetic field B are always perpendicular to each other.

(ii) Both are perpendicular to the direction of propagation k.

(iii) No material medium is required; EM waves can move through vacuum.
Thus radio, microwaves, light, X-rays and γ-rays are all parts of one EM spectrum.

Electromagnetic wave propagation showing perpendicular electric and magnetic fields

2. Calculate the wavelength of a radio wave of frequency 30 MHz propagating in space.

Ans: Given: Frequency =30 MHz

=30×10⁶ Hz

f=30 MHz

=30×10⁶ Hz

Speed of light =3.0×10⁸ m s⁻¹

c=3.0×10⁸ m s⁻¹

Step-wise solution:

λ = 3.0 × 10⁸ / 30 × 10⁶ m

Therefore the wavelength is 10 m.

3. What is the frequency range of (i) visible light, (ii) radio waves?

Ans: (i) Visible light extends from roughly 4.0×10¹⁴ Hz4.0×10¹⁴ Hz (red) to 7.5×10¹⁴ Hz7.5×10¹⁴ Hz (violet).

(ii) Radio waves start near 30 kHz and rise up to about 300 GHz, covering long-wave, medium-wave, short-wave, VHF, UHF, SHF and EHF bands.

INTEXT QUESTIONS 30.2

1. What is a coaxial cable? Write down its frequency range of operation.

Ans: A coaxial cable is a guided transmission line made of:

(i) A central solid (or stranded) inner conductor.

(ii) A concentric hollow cylindrical outer conductor (shield).

(iii) A uniform dielectric spacer between them.

Because the return current flows on the inner surface of the shield, external fields are screened and the signal remains inside the annular region. Coaxial lines exhibit low radiation loss and handle high frequencies up to about 3 GHz routinely; with special low-loss dielectrics they may work to ~40 GHz.

2. State the basic principle used for guiding light in an optical fibre.

Ans: Light remains confined in an optical fibre due to total internal reflection (TIR). The fibre core has slightly higher refractive index  n₁ than its cladding  n₂ . When a ray inside the core strikes the core-cladding interface at an angle greater than the critical angle =sin θc −1(2/1)

θc=sin⁻¹(n₂/n₁)

It reflects completely instead of refracting, bouncing repeatedly and carrying the signal with negligible loss.

Optical fiber structure showing core, cladding and light propagation by total internal reflection