AMIE Section A (IEB) Physics Question Paper October 2023 - ECourseFlix

Date: 04/12/2023

The Institution of Engineers, Bangladesh

AMIE SECTION "A" (OLD & NEW) EXAMINATION, OCTOBER 2023

Sub: Physics

Full Marks: 100

Time: 3 Hours

The figures in the margin indicate full marks.

There are SEVEN questions in this paper. Answer any FIVE.

Question 1

(a) Define degrees of freedom and state the law of equipartition of energy. 4

(b) Find the relation between the ratio of two specific heats, $\gamma$, and the degrees of freedom, $f$. Also find the values of $\gamma$ for diatomic and triatomic gases. 12

(c) If the molecular diameter of hydrogen is $1.9\times10^{-8}$ cm, find the number of collisions by a hydrogen molecule in 1 s, if temperature $T=300\text{ K}$ and pressure $P=1\text{ atmos}$. 4

Question 2

(a) What do you understand by the term "entropy"? Explain why the entropy of the universe is increasing. 8

(b) (i) Show that the entropy remains constant in an isolated reversible process. (ii) Write down the Maxwell's thermodynamic relations. 8

(c) 10 gm of water at $60^{\circ}\text{C}$ is mixed with 30 gm of water of $20^{\circ}\text{C}$. Calculate the change in entropy of the system. 4

Question 3

(a) Explain the terms: (i) Polarizing angle (ii) Optic axis, and (iii) double refraction. 6

(b) State and prove Brewster's law and Malus law. 10

(c) Two polarizing sheets have their polarizing directions parallel so that the intensity $I_m$ of the transmitted light is a maximum. Through what angle must either sheet be turned if the intensity is to drop by one-half? 4

Question 4

(a) Distinguish between reverberation and reverberation time. 4

(b) Give the theory of decay of sound inside a room and hence obtain an expression of reverberation time. 12

(c) The volume of a room is $600\text{ m}^3$. The wall area of the room is $220\text{ m}^2$, the floor area is $120\text{ m}^2$ and the ceiling area is $120\text{ m}^2$. The average sound absorption coefficient, (i) for the walls is 0.03, (ii) for the ceiling is 0.80, and (iii) for the floor is 0.06. Calculate the average sound absorption coefficient and the reverberation time. 4

Question 5

(a) Justify the statement "charge is conserved" with two examples. 4

(b) Consider an infinite line of charge whose linear charge density has the constant value $\lambda$. Calculate the electric field $E$ a distance $y$ from the line. 12

(c) An electric dipole consists of two opposite charges of magnitude $q=1.0\times10^{-6}\text{ C}$ separated by $d=2.0$ cm. The dipole is placed in an external field of $1.0\times10^5\text{ N/C}$. (i) What maximum torque does the field exert on the dipole? (ii) How much work must an external agent do to turn the dipole end for end starting from a position of alignment $(\theta=0)$? 4

Question 6

(a) Differentiate between damped and forced vibrations. 4

(b) Derive the differential equation for damped harmonic motion and solve it when the damping is small. 12

(c) A body oscillation with simple harmonic motion according to the equation: $x=6.0\cos(3\pi t+\pi/3)\pi$. Find the displacement and velocity at the time $t=2\text{s}$. 4

Question 7

(a) What do you understand by spherical aberration and chromatic aberration? 4

(b) Write short notes on: (i) astigmatism, (ii) coma, (iii) distortion, and (iv) curvature of the image. 12

(c) Two thin convex lenses of focal lengths 20 cm and 5 cm are placed 10 cm apart. Calculate the power of the equivalent lens. 4