Applied Physics in Engineering

First Semester - B.Tech. Degree Examination, April

Applied Physics in Engineering

Time: 2 hours                                                                                                  Max. Marks: 50

Note: All the objective questions are compulsory (Part A)

Answer any ONE full question from each module (Part B)

Answer any ONE full question (Part C)

 

Physical constants: Velocity of light, c = 3×10⁸ m/s; h = 6.63×10^-34Js; k = 1.38×10^-23J/K;

m_e = 9.1×10^-31Kg; e = 1.6×10^-19C.

Part A

1. The Richardson constant value with unit is

A) 1.2 × 10⁶ Am^-2 K                                                               B) 1.02 × 10⁶ Am^-2 K 

C) 1.21 × 10⁶ Am^-2 K                                                  D) None of these

           

2. The correct sequence of the following materials in the increasing order of magnetic susceptibility is

A) Diamagnetic – Ferromagnetic – Paramagnetic – Superconductor

B) Ferromagnetic – Paramagnetic – Diamagnetic – Superconductor

C) Paramagnetic – Diamagnetic – Superconductor – Ferromagnetic

D) Superconductor – Diamagnetic – Paramagnetic – Ferromagnetic

 

3. At high temperatures, a ferromagnet becomes

A) Diamagnet                                                             B) Soft Ferromagnet  

C) Paramagnet                                                                       D) Hard Ferromagnet

 

4. Quantum dot is a ______ entity

A) 3-dimensional       B) 2-dimensional        C) 1-dimensional                   D) 0-dimensional

 

5. The reason for narrow tube in He-Ne laser

A) Atomic collision with tube wall increases             B) Atomic collision with tube wall decreases

C) There is no effect of narrow tube on He-Ne          D) None of these

 

6. Which one of the following is not a type of LCD display?

A) Twisted Nematic                                                  B) In-Plane Switching 

C) Edge lit                                                                  D) Vertical alignment

 

7. LCD TV work on the principle of

A) Light blockage                                                       B) Emission of cathode rays  

C) Emission of cathode rays and light                        D) Light emission

 

8. APD is a photodiode where A stands for

A) Advanced              B) Aerial                     C) Atomic                               D) Avalanche

9. Erbium doped fibers have long _________ leading to coherent amplification.

A) Edges                     B) Metastable states    C) Connectors                         D) None of these

 

10. Light signals are transmitted through optic fibers by

A) Multiple total internal refraction                            B) Birefringence        

C) Dispersion                                                              D) None of these

 (10×1Mark)

Part B

Module 1

11 (a) Write a note on classification of magnetic materials. What is Hysteresis? Explain with the help of a graph.                                                                                                 (6Marks)

 (b) Write notes on Isotope effect and Critical field.                                                 (4 Marks)

OR

12 (a)   What is Fermi energy? Discuss variation of Fermi factor with energy and temperature.                                                                                                                                           (6 marks)

(b) A Josephson junction consists of two super conductors separated by a very thin insulating layer. When a DC voltage is applied across the junction an AC current is produced, a phenomenon called Josephson effect. Calculate the frequency of the AC current produced when a DC voltage of 1.5μV is applied.                                                                                   (4 Marks)

 

Module 2

13 (a) Obtain an expression for energy density of radiation under equilibrium condition in terms of Einstein co-efficients.                                                                                            (7 Marks)

(b) What are the three types of LCD display?                                                            (3 Marks)

OR

14 (a) With the help of energy level diagram, describe the construction and working of He-Ne laser.                                                                                                                                 (6 Marks)

(b) Write a note on recording of a hologram.                                                             (4 Marks)

 

Module 3

15 (a) Explain the working of Erbium doped fiber amplifier, EDFA.                       (6 Marks)

(b) An optical fiber of 600 m long has input power of 120 mW which emerges out with power 90 mW. Find attenuation in the fiber.                                                                                   (4 Marks)

OR

16 (a) Derive the expression for numerical aperture in an optical fiber.                     (6 Marks)

(b) Write a note on use of optical fiber for mechanical inspections.                           (4 Marks)

                                                                                               

Part C

17(a) Why cladding in an optical fiber is coated by a "buffer"?                                 (2 Marks)

(b) The electrical resistivity of copper at 27⁰C is 1.72×10^-8 Ωm. Compute the thermal conductivity if the Lorentz number is 1.12×10^-8 WΩK^-2.                                       (4Marks)

(c) What is the role of Helium in He-Ne laser?                                                            (4 Marks)

OR

18 (a) OFC play a crucial role in improving the quality and efficiency of medical care by enabling real-time communication, remote consultations, and accurate diagnosis. Explain.

 (6 Marks)

(b) The Fermi temperature of a metal is 24600K. Determine the Fermi velocity.      (4 Marks)