## Most Important Question Of Physics

**UNIT: Modern Physics**

**Lesson 1: Electrons & Protons**

**⚫Why electric discharge does not take place at very low pressure? (Take place at low pressure)**

**⚫Gases are insulator at ordinary pressure and start conducting at low pressure. Why?**

**⚫ The value of e/m is constant for cathode ray but not for positive ray? (Cathode ray are not electromagnetic ray. Why?)**

**⚫ Define: threshold frequency, stopping potential photoelectric effect, quantization of charge, cathode ray,**

**⚫ Millikan's oil drop experiment, JJ Thompson's experiment, Millikan's experiment to determine plank's constant, Einstein's photoelectric equation**

**⚫Numerical related to Millikan's experiment and photoelectric equation**

**Lesson 2: solids and semiconductor device**

**⚫ Define: Hole in semiconductors, nanotechnology, doping, truth table, logic gates, junction diode, rectifier, PN junction, Zener diode, transistor**

**⚫Working of full wave rectifier (figure) • Describe the formation of potential barrier and depletion region in PN junction**

**⚫Explain the biasing of junction diode Logic gates; NOT, OR, AND, NAND and NOR**

**⚫How is Zener diode is used as voltage regulator?**

**Lesson 3: Quantization of Energy**

**⚫AN electron and a proton have a same KE /speed/ potential difference. Which one of them has longer de Broglie wavelength.**

**⚫ State and explain Bragg's law**

**⚫ Define: population inversion, optical pumping, ionization energy, ionization potential, X-**

**ray, matter wave**

**⚫Uncertainly principle**

**⚫Production of X-ray**

**⚫ Bohr's postulate and total energy and radius of electron in nth orbit of H**

**⚫ State and explain uncertainty principle**

**⚫ Numerical based on Bragg's law and de Broglie wavelength**

**Lesson: 4 Radioactivity**

**Lesson Recent Trends in Physics**

**⚫ explain the origin of earthquakes**

**⚫Explain different types of internal waves: S and P-waves**

**Unit: Mechanics**

**Lesson 1: Rotational dynamics**

**⚫Derive the expression for rotational kinetic energy**

**⚫Describe the term moment of inertia and radius of gyration**

**⚫Find the moment of inertia of thin uniform rod rotating about its center and its one end**

**⚫ Establish the relation between torque and angular acceleration of a rigid body • Describe the work and power in rotational motion with expression**

**⚫ Define angular momentum and prove the principle of conservation of angular**

**momentum**

**⚫ Solve numerical problems and conceptual questions regarding the rotational dynamics**

**Lesson 2: Periodic Motion**

**⚫Define simple harmonic motion and state its equation.**

**⚫Derive the expressions for energy in simple harmonic motion Derive the expression for period for vertical oscillation of a mass suspended from coiled spring**

**⚫ Describe angular simple harmonic motion and find its period**

**⚫ Derive expression for period of simple pendulum**

**Lesson 3: Fluid Statics**

**⚫State and explain Archimedes principle and Pascal's law Define up-thrust, pressure in fluid, buoyancy, center of buoyancy and meta center**

**⚫State and use the law of floatation,**

**⚫Describe surface tension and explain its principle**

**⚫Establish the relation between surface energy and surface tension**

**⚫Define angle of contact and capillarity with examples**

**⚫State the Newton's Formula for viscosity of a liquid and define coefficient of viscosity**

**⚫Differentiate between laminar and turbulent flow & describe Reynolds number**

**⚫ Recall and use the Poiseuille's formula**

**⚫State Stoke's law and use it to determine the coefficient of viscosity of given liquid**

**⚫Explain equation of continuity and its application**

**⚫Recall the Bernoulli's equation and explain its uses**

**⚫ Solve the Numerical problems and conceptual questions regarding the fluid Statics.**

**Unit: Heat and Thermodynamics**

**Lesson 1: First Law of Thermodynamics**

**⚫ Define thermodynamic system, work done by the system, work done on the system, concept of latent heat and internal energy.**

**⚫ State and explain first law of thermodynamics limitations and necessity of second**

**law of thermodynamics**

**⚫Define and explain two specific heat capacities of gas appreciating the relation Cp-**

**Cv=R and Cp-Cv=r.**

**⚫ Explain various thermodynamic process (isothermal, isobaric, sochoric and**

**adiabatic) with good concept of their P-V diagram.**

**⚫Derive adiabatic equation PV^y=Constant.**

**⚫Drive expression for work done during isothermal and adiabatic process. Give concept of neversible and irreversible process with examples.**

**⚫Solve mathematical problems related to first lave of thermodynamics and**

**thermodynamic process**

**Lesson 2: Second Law of Thermodynamics**

**⚫State and explain second law of thermodynamics (Kevin's and Clausius's**

**statement).**

**⚫ Explain heat engine as a device to convert heat energy into mechanical energy appreciating that its efficiency is less than 100%.**

**⚫**

**Discuss Carnot's cycle with the concept of P-V diagram and calculate the work**

**done of each step and corresponding efficiency.**

**⚫Describe internal combustion engines, Otto engine and diesel engine with the help**

**of P-V diagram to compare their efficiencies.**

**⚫Explain refrigerator as heat engine working in reverse direction**

**⚫Introduce entropy as a measure of disorder appreciating its roles in thermodynamic process.**

**⚫Solve mathematical problems related to heat engine.**