CLASS-12-CBSE-BOARD-IMPORTANT-QUESTIONS-PHYSICS

 PHYSICS CLASS 12 PHYSICS IMPORTANT QUESTIONS CHAPTER-WISE CBSE AND STATE BOARDS

                           SUBJECT CODE – 042

Unit I – Electrostatics

Marks: 16

• Chapter 1: Electric Charges and Fields

• Chapter 2: Electrostatic Potential and Capacitance

UNIT II

Chapter 3: Current Electricity

Unit III – Magnetic Effects of Current and Magnetism

Marks: 17

Chapter 4: Moving Charges and Magnetism
Chapter 5: Magnetism and Matter

• Unit IV – Electromagnetic Induction and Alternating Currents

Chapter 6: Electromagnetic Induction
Chapter 7: Alternating Current

• Unit V – Electromagnetic Waves
• Marks: 18

Chapter 8: Electromagnetic Waves

• Unit VI – Optics

Chapter 9: Ray Optics and Optical Instruments
Chapter 10: Wave Optics

• Unit VII – Dual Nature of Radiation and Matter
• Marks: 12

Chapter 11: Dual Nature of Radiation and Matter

• Unit VIII – Atoms and Nuclei

Chapter 12: Atoms
Chapter 13: Nuclei

• Unit IX – Electronic Devices

Chapter 14: Semiconductor Electronics: Materials, Devices and Simple Circuits

• Total Marks: 70

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Unit I – Electrostatics

Marks: 16

QUESTION 1: What is the electrostatic potential due to an electric dipole at an equatorial point? (All India 2009)

QUESTION 2: What is the work done in moving a test charge q through a distance of 1 cm along the equatorial axis of an electric dipole? (All India 2009)

QUESTION 3: A point charge Q is placed at point O as shown in the figure. Is the potential difference VA – VB positive, negative, or zero if Q is

(i) positive
(ii) negative? (Delhi 2011)

QUESTION 3: The electric field inside the shell is zero. This implies that potential is constant inside the shell (as no work is done in moving a charge inside the shell) and, therefore, equals its value at the surface, which is 10 V.

QUESTION 4: Why is electrostatic potential constant throughout the volume of the conductor and have the same value (as inside) on its surface? (Delhi 2012)

QUESTION 6: Distinguish between a dielectric and a conductor (Comptt. Delhi 2012)

QUESTION 7: Why must the electrostatic potential inside a hollow charged conductor be the same at every point? (Comptt. All India 2012)

QUESTION 8: 

Two charges 2 µC and – 2µC are placed at points A and B 5 cm apart. Depict an equipotential surface of the system. (Comptt. Delhi 2013)

QUESTION 9

What is the amount of work done in moving a point charge around a circular arc of radius r at the centre of which another point charge is located? (Comptt. All India 2013)

QUESTION 10: Two equal balls having equal positive charges of ‘q’ coulombs are suspended by two insulating strings of equal length. What would be the effect on the force when a plastic sheet is inserted between the two? (All India 2014)

QUESTION 11: A charge ‘q’ is moved from a point A above a dipole of dipole movement ‘p’ to a point B below the dipole in the equatorial plane without acceleration. Find the work done in the process. (All India 2016)

QUESTION 12: Derive an expression for the potential energy of an electric dipole of dipole movement 

p⃗  in the electric field E⃗ 
(Delhi 2008)

QUESTION 13: Two point charges, 4Q and Q, are separated by 1 m in air. At what point on the line joining the charges is the electric field intensity zero?

Also calculate the electrostatic potential energy of the system of charges, taking the value of charge, Q = 2 × 10⁻⁷ C.

Unit I – Electrostatics

Marks: 16

Electrostatics deals with the study of electric charges at rest, electric fields, electric potential, and capacitance. This unit is highly important for Class XII board examinations.

Important Formulae (12)

1. Coulomb’s Law
F = (1 / 4πϵ₀) × (q₁q₂ / r²)

2. Electric Field Intensity
E = F / q

3. Electric Field due to a Point Charge
E = (1 / 4πϵ₀) × (q / r²)

4. Electric Dipole Moment
p = q × 2a

5. Electric Field due to a Dipole (Axial Line)
E = (1 / 4πϵ₀) × (2p / r³)

6. Electric Flux
Φ_E = E · A

7. Gauss’s Law
∮E · dA = q_enclosed / ϵ₀

8. Electric Potential
V = W / q

9. Electric Potential due to a Point Charge
V = (1 / 4πϵ₀) × (q / r)

10. Relation between Electric Field and Potential
E = − dV / dr

11. Capacitance
C = Q / V

12. Capacitance of a Parallel Plate Capacitor
C = ϵ₀A / d

Exam Tip: Practice numericals based on electric field and capacitance. Learn derivations of Coulomb’s law, Gauss’s law, and capacitors for scoring full marks.

QUESTION 14: Calculate the work done to dissociate the system of three charges placed on the vertices of a triangle as shown. (Delhi 2008)

QUESTION 14: (i) Can two equipotential surfaces intersect each other? Give reasons.

(ii) Two charges, -q and +q, are located at points A (0, 0, -a) and B (0, 0, +a), respectively. How much work is done in moving a test charge from point P (7, 0, 0) to Q (-3, 0, 0)? (Delhi 2009)

QUESTION 15: A network of four capacitors, each of capacitance 15 µF, is connected across a battery of 100 V, as shown in the figure. Find the net capacitance and the charge on the capacitor C4. (Comptt. Delhi & All India 2012)

QUESTION 16: A network of four capacitors, each of capacitance 30 pF, is connected across a battery of 60 V as shown in the figure.
Find the net capacitance and the energy stored in each capacitor. (Comptt. All India 2012)

QUESTION 17:  An electric dipole of length 4 cm, when placed with its axis making an angle of 60° with a uniform electric field, experiences a torque of 4√3 Nm. Calculate the potential energy of the dipole, if it has charge ± 8 nC. (Delhi 2014)

QUESTION 18: An electric dipole of length 2 cm, when placed with its axis making an angle of 60° with a uniform electric field, experiences a torque of
8 √3 Nm. Calculate the potential energy of the dipole, if it has a charge of ± 4 nC. (Delhi 2014)

QUESTION 19:A parallel plate capacitor of capacitance C is charged to a potential V. It is then connected to another uncharged capacitor having the same capacitance. Find out the ratio of the energy stored in the combined system to that stored initially in the single capacitor. (All India 2014)

QUESTION 20: (a) A charge +Q is placed on a large spherical conducting shell of radius R. Another small conducting sphere of radius r carrying charge ‘q’ is introduced inside the large shell and is placed at its centre. Find the potential difference between two points, one lying on the sphere and the other on the shell.

(b) How would the charge between the two flow if they are connected by a conducting wire? Name the device which works on this fact. (All India 2009)

QUESTION 21: A capacitor of unknown capacitance is connected across a battery of V volts. The charge stored in it is 300 µC. When potential across the capacitor is reduced by 100 V, the charge stored in it becomes 100 V. Calculate the potential V and the unknown capacitance. What will be the charge stored in the capacitor if the voltage applied had increased by 100 V? (Delhi 2013)

Question 22: Two uniformly large parallel thin plates having charge densities + σ and – σ are kept in the X-Z plane at a distance ‘d’ apart. Sketch an equipotential surface due to electric field between the plates. If a particle of mass m and charge q’ remains stationary between the plates, what is the magnitude and direction of this field? (Delhi 2011)

                                                              

                                                                                     

                                          Unit II current electricity

1. Explain the Kirchoff law.

2. Explain the basis of Kirchoff's law. (Law  of conservation of charge and energy)

3. Is Kirchoff law applicable to both AC and DC circuit? (yes)

4. Define the potential gradient of the potentiometer wire. (Potential difference per unit length of the potentiometer wire)

5. What is the difference in the voltameter and the potentiometer?

6. how the voltameter and ammeter differ?

7. calculate the shunt resistance when connected across the galvanometer of restance 18 ohm will allow 1/20 of the current to pass through galavanaometer.

8. Explain the meter brtidge with neat diagram.

9.  In a  metyer bridge balance is found  at 39.5 cm from an end , when resistor was  12.5 cm (right gap). Determine the resistance of the right part. Determine if X and R are interchanged.

What happens if the cell and the galvanometer was changed.

10. Explain the use of potetiometer to compare the emf of two cells.

11.Show on a graph the variation of resistivity with temperature for a typical semiconductor . (Delhi 2012)

12.Shown below is a closed electric circuit. Initially, the switch S is closed. If the switch S is now opened, what happens to the heat dissipated across R1?

A. Increases B. Decreases C. There is no change D. Cannot be determined without actual values

13. Assertion: If the charges are placed on an isolated conductor, it results in a zero electric field inside the conductor. On the other hand, a conductor connected to a source of emf, results in a steady current due to a constant electric field inside the conductor. Reason: A conductor is always in an electrostatic equilibrium whether or not it is connected to a source of emf. Select the correct option. 

A. Both A and R are true and R is the correct explanation of A

 B. Both A and R are true and but R is NOT the correct explanation of A 

C. A is true but R is false 

D. A is false and R is also false

14. In an electric circuit shown, a network of resistors is connected across a cell of emf 2V and internal resistance 0.5 ohm

(a) What is the total current drawn from the battery by the circuit? (b) What is the power consumed by the circuit from the battery?

 Question 13:        Two statements are given below. One is labelled Assertion (A) and the other is labelled Reason (R). Read the statements carefully and choose the option that correctly describes statements A and R. 

Assertion (A): The kinetic energy of a charged particle describing a circular path in a uniform magnetic field does NOT remain constant with time. 

Reason (R): The velocity of a charged particle moving in a circular path in a uniform magnetic field changes with time. 

A. Both assertion and reason are true and reason is the correct explanation for assertion.

 B. Both assertion and reason are true and reason is not the correct explanation for assertion. 

C. Assertion is true but the reason is false. 

D. Assertion is false but the reason is true. 

                                                       

                         Unit III – Magnetic Effects of Current and Magnetism

Question 1:

(i) State Biot-Savart’s law in vector form expressing the magnetic field due to an element dl carrying current 7 at a distance r from the element.

(ii) Write the formula for the magnetic field's strength at the center of a circle with radius r that is carrying a constant current of 7. Because of the current loop, draw the field lines.[All India 2014C]

Question 2: Using the formula for the magnetic force acting on a particle of charge q traveling at velocity v in a magnetic field B, define one tesla.

Question 3: The parallel planes with a common axis that passes through O include two identical circular loops, P and Q, each with radius r and equal currents. As can be observed from O, which is equally spaced from loops P and Q, the current flows clockwise in P and counterclockwise in Q. Determine the net magnetic field's strength at O.

Question 4: A current is carried by a long solenoid with N turns and length L. I. Determine the magnetic field's expression inside the solenoid. [All India 2008; 2011C]

Question 5: State the circuital law of Ampere. Give an example of how this law makes it simple to evaluate the magnetic field when the system has symmetry. [All India, 2010]

Question 6: State the circuital law of Ampere. Display the integral form of State Ampere's circuital law, (ii) As seen in the image, two long coaxial insulated solenoids and S2 of similar length are wound one over the other.A constant current travels via the inner solenoid Sx to the other end B, which is connected to the outer solenoid, where some current flows in the opposite direction to exit at end A. Determine the strength and direction of the net magnetic field at a point if nx and n2 are the number of rotations per unit length.

(a)inside on the axis and
(b)outside the combined system

Question 7:Is the magnetic field solely caused by a constant electric current? Explain your response.

Question 8: Why should a moving coil galvanometer's spring/suspension wire have a low torsional constant? [All India, 2008]

Question 9: Describe the galvanometer's voltage and current sensitivity. Justify your response. A galvanometer's voltage sensitivity may not always increase when its current sensitivity is increased.

Question 10: An axis that passes through the center and is perpendicular to the ring's plane is used to rotate a metallic rod of length / at a frequency v, with one end hinged at the center and the other at the circumference of a circular metallic ring of radius r. Everywhere there is a constant, uniform magnetic field B parallel to the axis. Explain how the emf is created between the center and the metallic ring using Lorentz force, and then derive its expression.[Delhi, 2013]

Question 11:Write the expression in vector form for the magnetic moment (m) caused by a planar square loop of side carrying a steady current. This loop is positioned in a horizontal plane close to a long, straight conductor that is carrying a constant current at a distance of l in the provided image. Explain why there will be a net force but no torque in the loop.

Question12: (i) Create a labelled schematic of a galvanometer with a moving coil. Give a brief explanation of its operation and principle.

(ii) Responds to the following queries.
(a) Why is a cylindrical soft iron core inserted into a galvanometer coil?
(b) A galvanometer's voltage sensitivity may not always increase when its current sensitivity is raised. Give justifications for your explanation.

Question 13: Draw the lines of the magnetic field caused by a current flowing through a long solenoid. To find the magnetic field caused by the current I in a long solenoid with n turns per unit length, apply Ampere's circuital law.

Question 14: A current I is carried by a circular coil with N turns and a diameter of d. It is unwound and rewound to create a second coil with a diameter of 2d and the same current. Determine the new coil's magnetic moment to that of the original coil.

Question 15: Determine the magnetic dipole moment of an electron circling the center nucleus.

Question 16: Where is the vertical component of the earth's magnetic field zero on its surface?

Question 17: Display the behavior of magnetic field lines diagrammatically when there is

both diamagnetic and paramagnetic materials. How can this unique characteristic be explained?

Question 18: The north point of a magnetic needle that is free to revolve in a vertical plane parallel to the magnetic meridian is at a 60° angle to the horizontal. The location's horizontal component of the earth's magnetic field is reported to be 0.4 G. Find out how strong the earth's magnetic field is there.

Question 19: An axis perpendicular to the direction of the homogeneous magnetic field B allows a tiny compass needle with magnetic moment M to rotate freely. I is the needle's moment of inertia with respect to the axis. The needle is released after being slightly jostled from its steady position. Show that it performs basic harmonic motion. Therefore, determine the phrase for its duration. (ii) At a certain location on Earth, a compass needle that is free to rotate in a vertical plane orients itself with its axis vertical. Determine the values of (a) the earth's magnetic field's horizontal component and (b) the dip's angle.

Question 20: The law of State Lenz. When a metallic rod is held horizontally in an east-west direction, gravity causes it to fall. Will its ends produce an electromagnetic field? Explain your response.

Question 21: An axis that passes through the center and is perpendicular to the ring's plane is used to rotate a metallic rod of length L at an angular frequency of co, with one end hinged at the center and the other at the circumference of a circular metallic ring of radius L. Everywhere there is a steady, uniform magnetic field B parallel to the axis. Find the expression for the electromagnetic field (emf) between the metallic ring and the center.

Question 22: .(i) Through an area where a uniform magnetic field is acting vertically downward, a rod of length / is transported horizontally with a uniform velocity v in a direction perpendicular to its length. Determine the expression for the induced emf across the rod's ends.

(ii) How can the Lorentz force operating on the conductor's free charge carriers be used to explain this motional emf? Describe.

Question 23: When a copper plate is allowed to oscillate between a magnet's two poles, its motion is dampened. What is causing this damping?

Question 24:When a copper plate is allowed to oscillate between a magnet's two poles, its motion is dampened. What is causing this damping?

Question 25:Determine the self-inductance of a long solenoid with N turns that contains a medium with relative permeability ur.

Question 26: (i) Create a schematic drawing of an AC generator that explains its fundamental components. Give a quick explanation of how it operates. Plot the changes in (a) magnetic flux and (b) alternating emf versus time produced by a wire loop spinning in a magnetic field. (ii) Why is a choke coil required when using fluorescent bulbs with AC mains?

Question 27: (i) Sketch an AC generator with labels and explain how it operates.

(ii) How does a generator's armature coil's magnetic flux change?
(iii) Determine the equation for the induced emf's highest value and state the rule that indicates its direction.
(iv) Display the change in the emf produced over time as the armature rotates in relation to the magnetic field's direction.

                                             

                                    

• Unit IV – Electromagnetic Induction and Alternating Currents

Question 1: Define self-inductance of a coil. Write its S.I. unit. (All India 2010)

Question 2: As seen in the illustration, two bar magnets are swiftly pushed in the direction of a metallic loop that is connected across a capacitor "C." Determine the capacitor's polarity.

Question 3: The arrow between two coils, PQ and CD, indicates the direction in which a bar magnet is moved. Determine which way each coil's induced current will flow. (All India, 2012)

Question 4: State Faraday’s law of electromagnetic induction. (Comptt. All India 2012)

Question 5: What happens to a pair of coils' mutual inductance when (i) the distance between them increases and (ii) the coils' number of turns increases (All India 2013)?
(i) Due to a drop in flux connected to the secondary coil, mutual inductance reduces.
(ii) Since M=μ0n1n2Al, mutual inductance (M) grows as n1 and n2 do.

Question 6: Two identical-sized spherical bobs, one made of glass and the other of metal, are free to descend from the same height above the ground. Which of the two would arrive first, and why? (2014, Delhi)

Question 7: Explain what "self-inductance" of a coil means. Put its S.I. Unit in writing. (All India, 2015)

Question 8: The arrow between two coils, PQ and CD, indicates the direction in which a bar magnet is moved. Determine each coil's induced current's direction (All India 2017).

Question 9: Two identical loops, one of copper and the other of aluminium, are rotated with the same angular speed in the same magnetic field. Compare

(i) the induced emf and
(ii) the current produced in the two coils. Justify your answer.(All India 2010)

Question 10: 
Describe the mutual inductance of two long coaxial solenoids. Determine the expression for the mutual inductance of an inner solenoid with length l, radius r1, and number of turns n1 per unit length caused by a second outer solenoid with the same length and number of turns n2 per unit length. Delhi (2011)

Question 11: As depicted in the picture, a rectangular loop PQMN with a moveable arm PQ of length 10 cm and resistance 2 Ω is put in a uniform magnetic field of 0.1 T acting perpendicular to the loop's plane. The arms MN, NP, and MQ have very little resistance. Determine the (i) induced emf in the arm PQ and (ii) induced current in the loop when the arm PQ is moved at a speed of 20 m/s. (Delhi Committee, 2014)

Question 12: Get the expression for the magnetic energy in terms of the magnetic field B, area A, and length l of the solenoid with n turns per unit length by starting with the expression for the energy w = 12LI2, stored in a solenoid of self-inductance L to build up the current I. Thus, demonstrate that B2/2µ0 is the energy density. (Delhi Committee, 2013)

Question 13: A coil with inductance L, capacitance C, and resistance R is linked in series with an alternating source of emf E = (Eo sin wt). Write an equation for the total impedance of the circuit (1).

(2) source emf frequency at which resonance occurs in the circuit conveying the current.

Question 14: A small town that needs 800 kW of 220 V electricity is 15 kilometers from a 440 V electric producing facility. The resistivity of the two power-carrying wirelines is 0.5 per kilometer. The town receives power from the line via a 4000-220 V step-down transformer located in a substation.
(a) Determine the line power loss caused by heat.

(b) How much electricity must the plant generate given a low power loss from leakage?

(c) Explain the step-up transformer in the plant.

Question 15: Explain the fundamental workings of an AC generator using a labeled diagram. When a coil with N turns and cross-sectional area A rotates perpendicular to the axis of rotation in a magnetic field B, find the expression for the induced electromagnetic field (EMF). For a graphic and a theory,

Question 16: Assertion (A): Current drawn through a long wire of finite resistance connected across an ac generator decreases when that wire is wound into a coil of many loops. Reason (R): Inductor offers back emf to the time varying ac current whereas a resistor doesn’t. Select the correct option. A. Both A and R are true and R is the correct explanation of A B. Both A and R are true but R is NOT the correct explanation of A C. A is true but R is false D. A is false and R is also false

Question 17: An a.c. source is shining with a specific brightness, and an electric lamp with a coil of negligible inductance is linked in series with a capacitor. When a lamp's (i) capacitance and (ii) frequency are reduced, how will its brightness change? Explain your response. Delhi (2009)

Question 18: Determine the impedance of an a.c. circuit with a resistor and an inductor. (Delhi, 2008)

Question 19: When a.c. current is applied to an ideal inductor, and the current lags behind the voltage in phase by π/2 radian. we can now write the instantaneous values.

Question 20: Describe a transformer's primary working principle.
How are transformers used to transmit electricity on a huge scale over vast distances? (All India, 2012)

•                       Unit V – Electromagnetic Waves

Question 1: Write X-rays, microwaves, UV rays, and radiowaves in ascending sequence according to their frequencies. Delhi (2009)

Question 2: Identify the electromagnetic radiation that contains waves with wavelengths between 10-2 m. Describe one application for this portion of the electromagnetic spectrum. Delhi (2009)

Question 3: Identify the electromagnetic waves that are utilized to analyze solid crystal structures. What range of frequencies does it have? (All India, 2009)

Question 4: What portion of the electromagnetic spectrum does the ozone layer absorb from sunlight? Delhi (2010)

Question 5: Which portion of the electromagnetic spectrum is utilized by radar systems?

Question 6:  Identify the portion of the electromagnetic spectrum with a wavelength between 10 and 10 m. Give it a single use. (All India, 2010)

Question 7: In a vacuum, a planar electromagnetic wave moves in the x-direction. What can you say about the vectors of the magnetic and electric fields? Delhi (2011)

Question 8: How do the vectors of the electric and magnetic fields relate to one another and to the direction in which electromagnetic waves propagate? (All India, 2012)

Question 9: A dc source has charged a capacitor. When it is fully charged, what are the displacement and conduction current magnitudes? (2013, Delhi)

Question 10: Write the electromagnetic wave speed relation in terms of the electric and magnetic field amplitudes. (All India, 2017)

Question 11: By = (8 × 10-6) sin [2 × 10-11 t + 300 π x] gives the oscillating magnetic field in a plane electromagnetic wave. T (i). Compute the electromagnetic wave's wavelength.

[ii] The expression for the oscillating electric field should be written down. (2008, Delhi)

Question 12: The formula for an electromagnetic wave's oscillating electric field is E = 30 sin [2 × 1011 t + 300 π x]. Vm-1

(a) Determine the electromagnetic wave's wavelength.
(b) Put the oscillating magnetic field's expression in writing. (Delhi, 2008)

Question 13:An external ac source is charging a capacitor composed of two parallel plates with plate area A and spacing d. Demonstrate that the current charging the capacitor is equal to the displacement current within it. (All India, 2012)

Question 14: (a) How do electromagnetic waves get created?

(a) How do you persuade yourself that momentum and energy are carried by electromagnetic waves? (Delhi Committee, 2012)

Question 14: (a) How do electromagnetic waves arise from an oscillating charge? Describe.

(b) Clearly illustrate the directions of the oscillating electric and magnetic field vectors in a sketch that illustrates the propagation of a planar em wave along the Z-direction. (Delhi Committee, 2012)

•                Unit VI – Optics

Question 1: If a plane wavefront is incident normally on the convex lens, sketch the refracted wavefront that emerges from it.

Question 2: Create a graph of the intensity distribution for diffraction caused by a single slit.

Question 3: What distinguishes an unpolarized light from a plane that is polarized tight?

Question 4:Which of these waves is capable of polarization? (i) Waves of heat (ii) Waves of sound? Provide a rationale for your response.

Question 5: If Young's double-slit device were submerged in water, what would happen?

Question 6:What does the term "plane polarized light" mean? What kind of waves exhibit the polarization property? Describe a process for creating a plane-polarized light beam.

Question 7: Brewster's state law. Brewster's angle varies depending on the color of the light in the transparent medium. Give an explanation. (CBSE Delhi, 2016)

Question 8: In Young's double-slit experiment, one of the slits is covered with semi-transparent paper to reduce light transmission. What impact will this have on the interference pattern?

Question 9: A monochrome source is positioned in front of a Polaroid (I). In front of this Polaroid (I), another Polaroid (II) is positioned and rotated until no light passes through. Now, a third Polaroid (III) is positioned between (I) and (II). Will light come out of (II) in this situation? Describe

Question 10: (i) Describe one characteristic that sets the interference phenomenon apart from the diffraction phenomenon.

(ii) A light beam with a wavelength of 600 nm is incident normally on a slit with a width of "a." Determine the slit's width if the distance between the slits and the screen is 0.8 m and the second-order maximum distance from the screen's center is 15 mm. (All India, 2008)

Question 11: (i) Describe the fundamental idea behind how an optical fiber operates.

(ii) What are the prerequisites for the occurrence of this phenomenon? (All India, 2009)

Question 12: (a) Why does the production of a persistent interference pattern require coherent sources?

(b) The intensity of light at a place on the screen where the path difference is X is K units in Young's double-slit experiment with monochromatic light of wavelength X. Determine the light intensity at a location where the path difference is 2λ/3. Delhi (2012)

Question 13: What distinguishes the interference fringes created in Young's double-slit experiment from a diffraction pattern caused by a single slit?

Question 14: (a) List the circumstances under which light sources are considered coherent.

(a) Why does the creation of an interference pattern require coherent sources? (All India, 2013)

Question 15: What does the term "wavefront" mean? Check the law of reflection using Huygen's wave theory. Alternatively, explain what a medium's "refractive index" is. When a plane wavefront is moving from a denser to a rarer medium, confirm Snell's law of refraction. (CBSE Delhi, 2019)

Question 16: Differentiate between linearly polarized and unpolarized light. Explain how scattering causes unpolarized light to become linearly polarized using a diagram. (CBSE Delhi, 2015)

                                             

Unit VI – Optics

Chapter 9: Ray Optics and Optical Instruments

Chapter 10: Wave Optics

Question 1: A liquid medium with the same refractive index is used to hold a converging lens with a refractive index of 1.5. How long would the lens's focal length be in this medium? (Delhi, 2008)

Question 2: Why does a clear sky tend to be bluish in color? (All India, 2008)

Question 3: When a glass prism with a refractive index of 1.5 is submerged in a liquid with a refractive index of 1.3, how does its angle of minimum deviation change? (All India, 2008)

Question 4: The angles of refraction in media A, B, and C are 15°, 25°, and 35°, respectively, for the same angle of incidence. Which medium would have the lowest light velocity? (All India, 2012)

Question 5: Water with a refractive index of 1.33 is submerged in a biconvex lens composed of a transparent material with a refractive value of 1.25. Will the lens exhibit divergent or converging behavior? Give an explanation. (All India, 2014)

Question 6: Create a ray diagram of a reflecting telescope. Give two reasons why this telescope is superior to a refracting telescope. (Delhi, 2008)

Question 7: Create a compound microscope's ray diagram. Put the expression's magnifying power in writing.

Question 8:In the near point position, create a labeled ray diagram of an astronomical telescope. Put the expression's magnifying power in writing.

Question 9: Create a ray diagram to show how an image is formed in a compound microscope. Put the expression's magnifying power in writing.

Question 10: When the angle of incidence is three-quarters of the angle of the prism, a light beam traveling through an equilateral triangular glass prism from air experiences the least amount of deviation. Determine how fast light travels through the prism.

Question 11: Describe a transparent medium's refractive index. A light beam travels through a triangle prism. Create a graph that illustrates how the angle of deviation varies with the angle of incidence.

Question 12: (i) Out of red and blue light, which is most distorted by a prism? Give an explanation.

(ii) Provide the formula for calculating a prism's material's refractive index under minimum deviation conditions.

Question 13: (a) It is known that convex and plane mirrors can create virtual representations of the things. To demonstrate how virtual objects can create real images in the instance of convex mirrors, draw a ray diagram.
(a) Why do cars utilize convex mirrors as side view mirrors?

(b) Why are convex mirrors used as side view mirrors in vehicles?

Question 15: Create a ray diagram that illustrates how a compound microscope creates images. Therefore, when the image is generated at infinity, obtain the expression for entire magnification.

Question 14:Draw a labelled ray diagram of a compound microscope. Why are the objective and the eye-piece chosen to have small focal length?

Question 15: On the face AB of an isosceles right-angled prism ABC, two monochromatic light rays are incident normally. For the two rays "T" and "2," the glass prism's refractive indices are 1.3 and 1.5, respectively. Once these rays have entered through the prism, follow their route.

Question 16: List the prerequisites for seeing a rainbow. Demonstrate your understanding of how a rainbow forms by creating appropriate diagrams.

Question 17: A tiny telescope has an eyepiece with a focal length of 5 cm and an objective lens with a focal length of 150 cm. What is the telescope's magnifying power when it is adjusted normally to view far-off objects?
What is the height of the tower's image created by the objective lens if this telescope is used to view a 100-meter-tall skyscraper three kilometers away?

Question 18:  On a right B-angled prism "abc" Q at face "ab," three light rays—red (R), green (G), and blue (B)—occur. For red, green, and blue wavelengths, the prism's material has R refractive indices of 1.39, 1.44, and 1.47, respectively. Which of the three color rays will come out of the "ac" face? Explain your response. Once these rays have passed through face "ab," follow their route.

Question 19: An observatory's massive refracting telescope has an objective lens with a focal length of fifteen meters. Determine the telescope's angular magnification if an eyepiece lens with a focal length of 1.0 cm is employed.
What is the diameter of the moon picture created by the objective lens if this telescope is used to observe the moon? The lunar orbit's radius is 3.8 × 106 m, while the moon's diameter is 3.42 × 10^ 6 m.

 Question 20: Create a ray diagram that illustrates how an object placed on the axis of a convex refracting surface with radius of curvature "R" forms an image by dividing the two media with refractive indices "n1 and n2" (n2 > n1). Determine the relationship n2v−n1u=n2−n1R using this diagram, where u and v stand for the object's and the image's respective distances. (Delhi Committee, 2012)

Question 21: A tiny bulb, which is thought to be a point source, is positioned at the bottom of an 80-cm-deep water tank. Determine how much of the water's surface can be illuminated by the lightbulb. Assume that water has a refractive index of 4/3. (Delhi Committee, 2013)

Question 22: (a) A point object with spherical faces with radii of curvature R1 and R2 is positioned in front of a double convex lens (with refractive index n = n2/n1 with respect to air). To create the actual image of the item, show the rays' path caused by refraction at the first and second surfaces.

Get the Lens-maker's formula for a thin lens as a result.
(b) The refractive index of a double convex lens with the same radius of curvature on both faces is 1-55. Determine the lens's radius of curvature needed to achieve a 20 cm focal length. (Comptt. All India)

                                                  Wave Optics

Quesation 1: What is the effect of increasing the distance between the slits on the angular separation of interference fringes in Young's experiment?

Question 2: When red light is used in place of the incident violet light, how does the glass prism's angle of minimum deviation change?

Question 3: Write the ratio of the intensities of the original light and the transmitted light after it has passed through the analyzer if the angle between the polarizer's pass axis and the analyzer is 45°.

Question 4:What kind of wavefront a (i) point source will produce, and

(ii) a far-off light source?

Question 5: At angle i, unpolarized light strikes a planar glass surface with a refractive index of µ. Write the relationship between angle i and refractive index µ if the reflected light becomes completely polarized.

Question 6: How will doubling the distance between the slits and screen affect the angular separation of interference fringes in Young's double slit experiment?


Question 7: What is the effect of doubling the distance between the slits and the screen on the fringe width in Young's double-slit experiment?

Question 8: What distinguishes plane polarized light from unpolarized light?

Question 9: Heat waves and sound waves are the two types of waves that can be polarized. Provide evidence to back up your response.

Question 10:Describe one characteristic that sets the interference phenomenon apart from the diffraction phenomenon.

Question 11: Describe one characteristic that sets the interference phenomenon apart from the diffraction phenomenon.
A parallel light beam with a wavelength of 600 nm typically strikes a slit with a width of "a." Determine the slit's width if the distance between the slits and the screen is 0.8 m and the second-order maximum distance from the screen's center is 15 mm.

Question 12: (a) Why does the production of a persistent interference pattern require coherent sources?
(b) The intensity of light at a place on the screen where the path difference is X is K units in Young's double-slit experiment with monochromatic light of wavelength X. Determine the light intensity at a location where the path difference is 2λ/3.

Question 13: Describe the two prerequisites for finding sources that are coherent.
Demonstrate that the bright and black fringes that appear on the screen are similarly spaced in Young's arrangement to create an interference pattern.

Question 14: (i) How does the interference pattern in a double-slit experiment relate to the diffraction from each slit?
(ii) A brilliant spot appears in the center of the obstacle's shadow when a small circular obstruction is positioned in the path of light from a distant source. Describe why.

Question 15: State Brewster’s law. The value of Brewster angle for a transparent medium is different for light of different colours. Give reason.

Question 16: A polaroid P1 is subjected to unpolarized light. Write the formula for the polarized beam passing through P2 when it passes through another polaroid P2 and its pass axis forms an angle of six with P1's pass axis. Create a plot that illustrates how intensity changes as θ changes between 0 and 2π.

Question 17: What is the definition of a wavefront? Draw a figure that illustrates how a plane wave propagates and reflects at the interface of two mediums using Huygen's architecture. Make sure the angle of incidence and the angle of reflection are equal.

Question 18: The two slits in Young's double-slit experiment are illuminated by monochromatic light with a wavelength of 600 nm, which creates an interference pattern with two successive brilliant fringes spaced 10 mm apart. The interference pattern where the two successive bright fringes are separated by 8 mm is produced by another source of monochromatic light. Determine the second source's light's wavelength. What happens to the interference fringes if a white light source is used in place of the monochromatic one?

Question 19: Young's double-slit experiment uses monochromatic light with a wavelength of 450 nm to illuminate two slits that are 0.15 mm apart. The distance between the screen and the slits is one meter.
(a) Determine how far the second (i) bright fringe and (ii) dark fringe are from the central maximum.
(b) If the screen is moved away from the slits, how will the fringe pattern alter?

Question 20: (a) Give a brief explanation of how the phenomena of polarization illustrates the transverse nature of light using an appropriate graphic.
(a) In what circumstances does unpolarized light become polarized when it travels from air to a transparent medium?

Question 21: Explain how a planar wavefront moves from a denser to a rarer medium using Huygens' principle. Thus, confirm Snell's law of refraction.

Question 22: (a) Explain how the intensity of diffraction pattern changes as the order (n) of the diffraction band varies.
(b) Two wavelengths of sodium light 590 nm and 596 nm are used in turn to study the diffraction at a single slit of size 4 mm. The distance between the slit and screen is 2 m. Calculate the separation between the positions of the first maximum of the diffraction pattern obtained in the two cases. (Comptt. All India 2015)

                    Unit VII – Dual Nature of Radiation and Matter

Question 1: The figure shows a plot of three curves a, b, c, showing the variation of photocurrent vs. collector plate potential for three different intensities I1, I2 and I3 having frequencies V1, v2 and v3 respectively incident on a photosensitive surface.

Point out the two curves for which the incident radiations have same frequency but different intensities.

Question 2: In a photoelectric effect experiment, 1.5 V is the stopping potential. What is the photoelectrons' maximal kinetic energy?

Question 3. Describe the "intensity" of radiation in the photon image of light.

Question4 :hy can't photoelectric emission occur at every frequency?

Question 5: When a charged particle with mass "m" and charge "q" is propelled by a potential V, write the expression for the de Broglie wavelength associated with that particle.

Question 6: The stopping potential for two photosensitive metals, A and B, is plotted against the frequency of incident radiation. Which of the two has a greater work-function value? Explain your response. (All India, 2014)

Question 7: In the photon picture of light, identify one factor that affects light intensity.

Question 8:  How does the stopping potential supplied to a photo cell change if the distance between the light source and the cathode is doubled?

Question 9: A potential difference of 100 volts accelerates an electron. What is the corresponding de-Broglie wavelength? Which region of the electromagnetic spectrum does this wavelength value relate to?

Question 10: The same potential accelerates both a proton and an a-particle from rest. Determine the de-Broglie wavelength ratio between them.

Question 11: Write the photoelectric equation proposed by Einstein. Clearly state the three key aspects of the photoelectric effect that can be explained using the equation above.

Question 12:The same accelerating potential accelerates both a proton and a deuteron. Which of the two has (a) a higher de-Broglie wavelength and (b) less momentum?
Provide justifications for your response.

Question 13: (i) Monochromatic light of frequency 6.0 × 1014 Hz is produced by a laser. The power emitted is 2.0 × 10-3 W. Estimate the number of photons emitted per second on an average by the source.
(ii) Draw a plot showing the variation of photoelectric current versus the intensity of incident radiation on a given photosensitive surface

Quuestion 14: To produce photoelectric emission, two monochromatic radiations with the same intensity and frequency v1 and v2 (V1 > v2) are incident on a photosensitive surface. Describe the situation in which (i) more electrons will be released and (ii) the maximal kinetic energy of the released photoelectrons will be greater, along with your reasoning.

Question 15: A metal X has a work function (W) of 3 × 10-19 J. Determine how many photons (N) of light with a wavelength of 26.52 nm have a total energy of W.

Question 16: (a) Give a brief explanation of the experimental methods used to establish the wave character of moving electrons.
(b) Calculate the de-Broglie wavelength ratio for a-particles and deuterons when they are

                                                                    

                                                  Unit VIII – Atoms and Nuclei

Question1. The de-Broglie wavelength of an electron and an alpha particle is the same. What is the relationship between their kinetic energies?
Question 2: Describe the nuclear force's distinctive characteristics.

Question 3: The mass numbers of two nuclei are 8:125. What is the nuclear radius ratio between them?
Question 4: The mass numbers of two nuclei are 1:3. What is the nuclear density ratio between them?

Question 5: Write the relationship between a radioactive nucleus's half life and decay constant.
Question 6: Can you tell the difference between nuclear fusion and fission? Describe the release of energy in both processes. (All India Committee, 2017)

Question 7:State the law of radioactive decay.

Plot a graph showing the number (N) of undecayed nuclei as a function of time (t) for a given radioactive sample having half life T1/2. Depict in the plot the number of undecayed nuclei at
(i) t = 3 T1/2 and
(ii) t = 51/2.(DeIhi 2009)

Question 8:(i) What feature of nuclear force accounts for the stability of binding energy per nucleon (BE/A) in the mass number "A" range of 30 < A < 170?

(ii) Demonstrate that, regardless of mass number A, the density of nuclei throughout a broad range of nuclei is constant.

Question 9: (i) For nuclei with mass numbers (A) between 30 and 170, why is the binding energy per nucleon determined to remain constant?

(ii) Energy is released when a heavy nucleus with mass number A = 240 splits into two nuclei, A = 120.
(iii) It is discovered to be very challenging to detect neutrinos (or antineutrinos) experimentally in β-decay. (All India Committee, 2011)

Question 10: (a) Write the fundamental nuclear process that a radioactive nucleus uses to emit β+ in a symbolic manner.

(b) In the following reactions:
Class 12 Physics Important Questions Chapter 13: Nuclei Class 12 Important Questions 71
Determine the values of a, b, c, and x, y, and z. (All India, 2017)

                                              

                                                    Unit IX – Electronic Devices

Question 1: Why should a reverse bias be used when operating a photodiode? (All India, 2008)
The fluctuation in reverse saturation current is more noticeable because the fractional change in minority charge carriers is greater than the fractional change in majority charge carriers.

Question 2:Give the logic symbol of NOR gate

Question 3: Give the symbol of NAND gate

Question 4:  Give an example og AND gate

Question 5:  Write the truth table of a two point input NAND gate.

Question 6: Differentiate between p-type and intrinsic semiconductors. Explain why, despite nh >> ne, a p-type semiconductor crystal is electrically neutral.

Question 7: A NOT gate receives the output of a 2-input AND gate. Provide the combination's name and logic symbol. Put its truth table in writing. Delhi (2009)

Question 9:

(i) Determine which logic gates in the provided logic circuit are designated P and Q.
(ii) Record the results at X for the inputs A = 0, B = 0, and A = 1, B = 1.

Quesion 10: configuration. Describe in detail how a transistor's active portion of the VD vs V curve is employed as an amplifier.

Question 11: Using a circuit schematic, briefly explain how emitter-base junction forward biasing and base-collector junction reverse biasing control the flow of current carriers in a p-n-p transistor.

Question 12: Describe how a photo-diode operates using a circuit diagram. Write a brief description of how the optical signals are detected.

Question 13: Give a brief explanation of the fundamental idea behind a transistor oscillator. Create a circuit schematic that illustrates how inductive coupling is used to provide feedback. Describe the oscillator's operation.

Question 14: Provide an n-p-n transistor circuit diagram for a common emitter amplifier. Sketch the signal's input and output waveforms. Write the voltage gain expression.

Create the energy band diagrams for (i) n-type and (ii) p-type semiconductors at T > OK. The donor level in an n-type Si semiconductor is marginally below the bottom of the conduction band. In contrast, the aceceptor energy level in a p-type semiconductor is marginally higher than the top of the valence band. Describe the function of these energy levels in the valence and conduction bands.