### Exam Year

Tribhuvan University

Institute of Science and Technology

2075

Bachelor Level / first-semester / Science

Computer Science and Information Technology( PHY113 )

Physics

Full Marks: 60 + 20 + 20

Pass Marks: 24 + 8 + 8

Time: 3 Hours

Candidates are required to give their answers in their own words as far as practicable.

The figures in the margin indicate full marks.

Group A

Attempt any two questions. (2 X 10 = 20)

1

Explain the process of semiconductor purification by describing the terms zone refining, single crystal growth, and scheme of IC production. Give an account of electronic component fabrication on a chip.

2

Set up a differential equation for an oscillation of a spring using Hooke’s and Newton’s second law. Find the general solution of this equation and hence the expressions for the period, velocity, and acceleration of oscillation.

3

Describe Frank-Hertz experiment. Interpret how the results of this experiment advocate atomic model proposed by Bohr?

4

Discuss Magnetic dipole moment. What is its effect on atom and on molecules? Explain.

Group B

Attempt any Eight questions. (8 X 5 = 40)

5

Explain Bloch theorem? Discuss its use in the Kronig-Penny model and hence in band theory.

6

Explain the construction and working of bipolar junction transistor (BJT)

7

A large wheel of radius 0.4m and moment of inertia 1.2 kgm2, pivoted at the center, is free to rotate without friction. A rope is wound around it and a 2kg weight is attached to the rope, when the weight has descended 1.5m from its starting position, (a) what is its downward velocity? (b) what is the rotational velocity of the wheel?

8

An electron is placed midway between two fixed charges, q1 = 2.5 × 10-10 C and q2 = 5 × 10-10 C. If the charges are 1 m apart, what is the velocity of the electron when it reaches a point 10cm from q2?

9

A small particle of mass 10-6 gm moves along the x-axis; its speed is uncertain by 10-6 m/s. (a) What is the uncertainty in the x coordinate of the particle? (b) Repeat the calculation for an electron assuming that the uncertainty in its velocity is also 10-6 m/s. Use the known values for electrons and Planck’s constant.

10

What is the probability of finding a particle in a well of width ∝ at a position $$\frac{\alpha }{4}$$ from the wall if n = 1, if n = 2, if n = 3. Use the normalized wavefunction ψ(x,t) =$$\left ( \frac{2}{a} \right )^{\frac{1}{2}}$$ sin$$\left ( \frac{n\pi x}{a} \right )e^{-\frac{iEt}{h cut}}$$.

11

Assuming that atoms are in a crystal structure and arranged as close-packed spheres, what is the ratio of the volume of the atoms to the volume available for the simple cubic structure? Assume a one-atom basis.

12

The output of a digital circuit (y) is given by this expression: $$y=(CB + \overline{C}A)(\overline{BA})$$ where A,B and C represent inputs. Draw a circuit of the above equation using OR, AND and NOT gate and hence find its truth table.