Engineering Physics Exam Questions and Answers: Units 3 & 4

Here are short, exam-oriented answers in English for all the questions shown in your notebook.

Unit 3: Physics Exam Questions

1) Write Short Notes on PIN Diode

A PIN diode is a semiconductor diode with three layers: P-type, Intrinsic (I), and N-type.

Features:

• Wide depletion region due to the intrinsic layer.
• Low capacitance.
• Works at high frequencies.

Applications:

• RF switches
• Microwave circuits
• Photodetectors
• Attenuators

2) Applications of Hall Effect

The Hall Effect is used to:

• Measure magnetic fields.
• Identify semiconductor type (P-type or N-type).
• Measure carrier concentration.
• Sensing electrical current.
• Speed and position sensors in automobiles.

3) What is De Broglie's Hypothesis?

De Broglie stated that every moving particle has a wave nature.

The wavelength is given by:

\[ \lambda = \frac{h}{p} = \frac{h}{mv} \]

Where:

• λ = wavelength
• h = Planck's constant
• m = mass
• v = velocity

Importance:

It proves the wave-particle duality of matter.

Unit 4: Physics Exam Questions

1) Working and V-I Characteristics of Tunnel Diode

Working:

A tunnel diode is a heavily doped PN junction diode. It works due to quantum tunneling.

• At low forward voltage, current increases rapidly.
• Current reaches Peak Current (I_p).
• As voltage increases further, current decreases (Negative Resistance Region).
• After Valley Current (I_v), current increases normally again.

V-I Characteristics:

• Forward region
• Peak current (I_p)
• Negative resistance region
• Valley current (I_v)
• Normal conduction region

Applications:

• High-speed switching
• Oscillators
• Microwave amplifiers

2) What is a Tunnel Diode?

A Tunnel Diode is a heavily doped PN junction diode that operates using the quantum tunneling effect and exhibits negative resistance.

3) Define and Explain the Hall Effect

Definition:

When a current-carrying conductor or semiconductor is placed in a magnetic field perpendicular to the current, a voltage develops across it. This is called the Hall Effect.

Uses:

• Magnetic field measurement
• Current sensors
• Position sensors
• Semiconductor testing

4) State Heisenberg Uncertainty Principle

It is impossible to determine both the exact position and exact momentum of a particle at the same time.

\[ \Delta x \Delta p \ge \frac{h}{4\pi} \]

5) Schrödinger Time-Dependent & Independent Equations

Time-Dependent Equation:

\[ i\hbar \frac{\partial \psi}{\partial t} = -\frac{\hbar^2}{2m}\nabla^2\psi + V\psi \]

Time-Independent Equation:

\[ -\frac{\hbar^2}{2m}\nabla^2\psi + V\psi = E\psi \]

6) What is Quantum Computing?

Quantum computing is a computing technology that uses quantum mechanics to process information.

It uses qubits instead of classical bits.

Advantages:

• Faster computation
• Solves complex problems
• Better optimization

7) What is a Qubit?

A Qubit (Quantum Bit) is the basic unit of quantum information.

Unlike a classical bit (0 or 1), a qubit can exist in 0, 1, or both simultaneously (superposition).

8) Applications of Quantum Computing

• Cryptography
• Drug discovery
• Artificial Intelligence
• Weather forecasting
• Financial modeling
• Optimization problems

9) Difference Between SEM and TEM

10) State the Following Terms

(i) Backscattered Electrons (BSE)

Electrons reflected from the sample surface after collision with atoms. Use: Composition and atomic number contrast.

(ii) Secondary Electrons (SE)

Low-energy electrons emitted from the sample surface. Use: Surface topography.

(iii) X-rays

Produced when high-energy electrons strike the sample. Use: Elemental analysis (EDS/EDX).

11) Electron Microscope and Its Types

Electron Microscope:

An electron microscope uses a beam of electrons instead of light to produce highly magnified images.

Advantages:

• Very high magnification
• High resolution
• Nanometer-scale imaging

Types:

1. SEM (Scanning Electron Microscope) – Studies surface structure.
2. TEM (Transmission Electron Microscope) – Studies internal structure.

These answers are suitable for 5–7 marks in Engineering Physics and are written in simple exam language.