# Frequently asked question|| Physic class 12

## Heat and Thermodynamics

Define first law of thermodynamics with its limitations

Adiabatic and isothermal condiations of thermodynamics

Wave and Optics

1. Define wave motion.
1. Derive the progressive wave equations in a medium.
2. Starting with the definition of stationary waves, prove that the distance between any two consecutive nodes or antinodes in a stationary wave is λ2.
3. Write an expression for the Newton’s formula for the velocity of sound in air. Explain the necessary correction made by Laplace.
4. Define end correction.
1. Show that, in open organ pipe, both odd and even harmonics can be produced.
5. Define natural frequency.
1. Describe an experiment to determine the velocity of sound in air by resonance air column tube method.
6. Describe sound wave as a pressure wave and deduce an expression for the pressure amplitude.
7. Define beats.
1. Obtain an expression for the beat frequency produced by the superposition of two waves of slightly different frequencies.
8. What is Doppler effect in sound?
1. Obtain an expression for the apparent frequency of sound when both source and observer are moving towards each other.
9. State Huygen’s law and use it to verify Snell’s law.
10. Describe Michelson’s method to determine the velocity of light.
11. Define coherent sources of light.
1. Describe Young’s double slit experiment and show that the bright fringes and dark fringes are equally spaced.
12. Define polarization of light.
1. Show that, μ=tanθp, where the symbols have their usual meanings.

## Electricy And Magnesium

1. How can you convert a galvanometer into ammeter (or voltmeter)? Explain.
2. Discuss the mechanism of metallic conduction.
1. Derive a relation between current density and drift velocity. i.e., I=neAvd.
3. State and apply Kirchoff’s rule to measure the unknown resistance of a wire by using wheatstone bridge circuit.
4. State the principle of meter bridge.
1. Describe how it is used to determine the resistance of a wire.
5. What is the principle of potentiometer?
1. Explain with necessary theory how you would determine the internal resistance of the internal resistance of a cell using this principle.
6. What do you mean by thermo electric effect?
1. Discuss the variation of thermo emf in a thermo couple with the change in temperature.
7. State and explain Biot – Savart’s law.
1. Use it to find the magnetic field due to a long straight current carrying conductor.
8. State Ampere’s law.
1. Deduce an expression for the force between two parallel current carrying wires.
9. State Faraday’s law of electromagnetic induction.
1. Derive an expression for the emf induced in a straight conductor moving at right angles to the direction of a uniform magnetic field.
10. State Faraday’s law of electromagnetic induction.
1. Deduce an expression for the emf induced in a coil rotating uniformly in a uniform magnetic field.
11. Explain the principle and working of a transformer.
12. Discuss the condition for resonant frequency of LCR alternating current circuit.

## Modern Physics

1. Describe about construction and working principle of Millikan’s oil drop experiment to determine the charge of an electron.
2. Define cross field.
1. Describe construction and working principle of J.J. Thomson’s experiment to determine specific charge of an electron.
3. Define threshold frequency and work function of a metal.
1. Explain Einstein’s photoelectric equation.
4. Describe the experiment to determine the Planck’s constant.
5. State Bohr’s postulates for atomic model.
1. Derive the expression for radius of an electron bound to hydrogen atom
6. Explain Bragg’s law of diffraction for X – rays.
7. What is zener breakdown.
1. How can a zener diode be used as a voltage regulator? Explain.
8. Define mass defect.
1. Explain the significance of graph of binding energy per nucleon versus atomic mass number.
9. State the laws of radioactivity. Derive the relation between half-life period and decay constant.

They are not a fixed questions that comes in exam but they are the possible questions and all the students are requested to also study this as well.