# Very Important Long Questions Collection – All Unit | Physics Class 12

## HSEB Exam | Questions Collection Very Important Long Questions Collection For: Science | Physics Class 12 From: All Unit

We have listed some very Important Questions. The repeating frequency of this questions are Comparatively High. This questions are asked on lots of previous papers.

Disclaimer: This questions are neither guessed nor we guarantee the possibility in the coming exam. This questions are often repeated in the previous exam only.

Unit One: Wave and Optics

1. What are stationary waves? Derive an equation for such a wave. [2060]
2. What the principle of superposition is as applied to wave motion? Discuss the result of superposing two waves of equal amplitude and same frequency travelling in opposite direction. [2068]
3. How is a progressive wave different from a stationary wave? Derive a progressive wave equation. [2070 ‘D’]
4. What is Newton’s formula for the velocity of sound? What correction was made by Laplace? [2053]
5. Describe the various modes of vibrations of the air column in an organ pipe. [2054]
6. What is Doppler’s effect? Derive an expression for the apparent frequency received by a stationary observer when a source is moving away from him. [2057]

Unit Two: Physical Optics

1. State and explain Huygens’s principle to show that a plane wave front incident obliquely on a plane mirror is reflected as a plane wave front so that the angle of incidence is equal to the angle of reflection. [2060, 2068]
2. Define Michelson’s method to determine the speed of light. Write advantages of this method over Foucault’s method. [2067]
3. What are coherent source? Prove analytically that the bright and dark fringes in young’s double slit experiment are equally spaced. [2060]
4. Describe Young’s double slit interference experiment to determine the wavelength of the source of light. [2069]
5. What do you mean by polarization of light? Show that tanθp = np where θp is the angle of polarization and Ƞ is the refractive index of the transparent medium. [2059]

Unit Three: Electricity and Magnetism

1. What do you mean by a shunt? Describe its use in converting a galvanometer into an ammeter. [2057]
2. What is drift velocity of an electron? Derive a relation between the current through a metallic conductor and the drift velocity in terms of the number of free electrons per unit volume of the conductor. [2059]
3. State and explain Ohm’s law. [2064]
4. What is potentiometer? Explain how do you compare emf of two cells using potentiontiometr. [2058]
5. What is a Wheatstone bridge? Obtain the balanced condition for the bridge. Explain how resistance can be measured by a meter bridge. [2068]
6. Explain, what do you mean by seebeck effect? How does thermoelectric emf vary with the temperature? [2057]
7. State and explain Faraday’s laws of electrolysis. Hence. Define Faraday’s constant. [2058]
8. Define the formula for the magnetic field at the centre of a circular coil carrying current. Explain why the magnetic field at the centre of the coil disappears when the circular coil is made infinitely large. [2059]
9. Derive an expression for the torque experienced by a current carrying rectangular coil placed in a uniform magnetic field and hence define magnetic dipole moment of the coil. [2060]
10. Derive an expression of force per unit length between two parallel conductors separated by a distance ‘r’ and carrying currents I1 and I2 in the same direction. [2066]
11. Define magnetic susceptibility and relative permeability and establish a relation between them. [2070 ‘C’]
12. Obtain the expression for the emf induced in the conductor moving in a magnetic field. [2052]
13. State and explain Faraday’s law of electromagnetic induction. [2067]
14. An alternating e.m.f is applied across a capacitor. Show that the current in it leads to the applied e.m.f. by 90°.

Unit Three: Modern Physics

1. Describe with necessary, theory, Millikan’s oil drop experiment to determine the value of the charge associated with an electron. [2052, 2068, 2069]
2. Describe an experiment to determine the specific charge of electron. [2054]
3. Explain the phenomenon of discharge of electricity through gases at low pressure. [2056]
4. Show that electron motion in magnetic field is circular. Prove that frequency and time period are independent with the velocity of electron. [2063]
5. How are P-type and N-Type semiconductors formed? Discuss the forward biasing of a P-N junction diode. [2060]
6. What is p-n-p transistor? Describe briefly a circuit of p-n-p transistor amplifier in its common emitted configuration. [2062]
7. What is Zender breakdown? Describe how a Zender diode can be used as a voltage regulator? [2070 ‘C’]
8. What are X-rays? Confirm with experiment the wave nature of X-rays. [2055]
9. What are Bohr’s postulates? Derive the formula for the radius of the third Bohr’s orbit. [2059]
10. What are the postulates of Bohr atomic model? Obtain an expression for the energy of nth orbit of hydrogen atom. [2064]
11. State and explain Einstein’s mass energy relation with example. [2052]
12. Discuss fission and fusion with an example of each. In which reaction is the energy released greater? [2070 ‘C’]
13. Explain the term “artificial radio-isotopes”. [2054, 2054]
14. Discuss energy crisis in a modern society. [2062]
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