Class 12 Physics has two very different faces- one is conceptual (laws, definitions, derivations) and the other is numerical (formulas, calculations, units). Most students don’t struggle because the subject is hard; they struggle because they don’t know which questions actually deserve their limited revision time before the exam.
This guide fixes that. Below you’ll find:
- Chapter-wise important questions (conceptual + numerical)
- Answers and step-by-step solutions
- Important formulas you’ll need for each chapter
- A separate high-value numerical question bank
- A quick list of important derivations
- A downloadable PDF for last-minute revision
Let’s go chapter by chapter.
Class 12 Physics Important Questions – Chapter-Wise
These questions are picked around the concepts that get tested most often, the numerical patterns that repeat every year, and the areas examiners typically use to check real understanding — not just memory. Use them to test yourself, not just to read through.
Electric Charges and Fields – Important Questions
Conceptual Questions
- Why does a charged body attract a small piece of uncharged paper?
Because the electric field of the charged body induces opposite charges on the near side of the neutral paper (polarisation), and the attractive force on the nearer, opposite charge is slightly stronger than the repulsive force on the farther, similar charge. - Why can electric field lines never cross each other? If two field lines crossed, the field at that point would have two directions at once, which is impossible since the electric field at any point has a single, unique direction.
- State Gauss’s law and mention one situation where it makes calculating the electric field much easier.
Gauss’s law states that the total electric flux through a closed surface equals 1/ε₀ times the charge enclosed. It simplifies field calculations for highly symmetric charge distributions, such as a uniformly charged infinite sheet, sphere, or long straight wire. - Why is the electric field inside a conductor always zero in electrostatic equilibrium?
Free charges inside a conductor rearrange themselves until the internal field cancels out; if any field remained, charges would keep moving, which contradicts equilibrium.
Numerical Questions
Q1. Two point charges of +2 μC and +6 μC are placed 30 cm apart in air. Find the electrostatic force between them.
- Given: q₁ = 2 × 10⁻⁶ C, q₂ = 6 × 10⁻⁶ C, r = 0.3 m
- Formula: F = k q₁q₂ / r², where k = 9 × 10⁹ N·m²/C²
- Calculation: F = (9 × 10⁹ × 2 × 10⁻⁶ × 6 × 10⁻⁶) / (0.3)² = (9 × 10⁹ × 12 × 10⁻¹²) / 0.09
- Final Answer: F = 1.2 N (repulsive)
Q2. A uniformly charged sphere has a surface charge density σ. Using Gauss’s law, derive the expression for the electric field outside the sphere at a distance r from its centre (r > R).
- Using a spherical Gaussian surface of radius r: E × 4πr² = Q/ε₀, so E = Q / (4πε₀r²) — the sphere behaves as if the entire charge is concentrated at its centre.
Important Formulas: Coulomb’s law F = kq₁q₂/r², Electric field E = F/q, Electric field due to a dipole (axial and equatorial), Gauss’s law φ = Q_enc/ε₀, Field due to an infinite sheet E = σ/2ε₀.
Electrostatic Potential and Capacitance – Important Questions
Conceptual Questions
- Why is no work done in moving a charge on an equipotential surface?
Because the potential difference between any two points on the surface is zero, and W = qΔV = 0. - Why does the capacitance of a parallel plate capacitor increase when a dielectric is inserted?
The dielectric gets polarised, reducing the net electric field between the plates for the same charge, which increases capacitance (C = Q/V). - What happens to the energy stored in a capacitor if it’s disconnected from the battery and then the plate separation is increased?
Charge stays constant, so energy (U = Q²/2C) increases as capacitance decreases.
Numerical Questions
Q1. A parallel plate capacitor has plates of area 200 cm² separated by 2 mm in air. Find its capacitance.
- Given: A = 200 × 10⁻⁴ m², d = 2 × 10⁻³ m, ε₀ = 8.85 × 10⁻¹² F/m
- Formula: C = ε₀A/d
- Calculation: C = (8.85 × 10⁻¹² × 200 × 10⁻⁴) / (2 × 10⁻³) = 8.85 × 10⁻¹¹ F
- Final Answer: C ≈ 88.5 pF
Q2. Three capacitors of 2 μF, 3 μF, and 6 μF are connected in series. Find the equivalent capacitance.
- Formula: 1/C = 1/C₁ + 1/C₂ + 1/C₃ = 1/2 + 1/3 + 1/6 = 1
- Final Answer: C = 1 μF
Important Formulas: V = kq/r, C = Q/V, series/parallel combination rules, Energy U = ½CV² = ½QV = Q²/2C, Capacitance with dielectric C = Kε₀A/d.
Current Electricity – Important Questions
This chapter is numerical-heavy, so focus on choosing the right method, not just plugging in numbers.
Conceptual Questions
- Why does the resistance of a conductor increase with temperature (for most metals)? Increased thermal vibration of ions increases collision frequency of free electrons, reducing relaxation time and increasing resistivity.
- Why are cells connected in series for high voltage requirements and in parallel for high current requirements? Series connection adds up EMFs (useful for voltage); parallel connection reduces effective internal resistance, allowing higher current delivery.
- State Kirchhoff’s junction rule and loop rule. Junction rule: the sum of currents entering a junction equals the sum leaving it (charge conservation). Loop rule: the algebraic sum of potential differences around any closed loop is zero (energy conservation).
Numerical Questions
Q1. A wire of resistance 10 Ω is stretched to double its length. Find its new resistance (assume volume remains constant).
- Concept: R ∝ l²/V when volume is constant (since R = ρl/A = ρl²/(A·l) = ρl²/V)
- Calculation: New length = 2l, so new R = 10 × (2)² = 40 Ω
- Final Answer: R_new = 40 Ω
Q2. In a Wheatstone bridge, resistances of 4 Ω, 6 Ω, 8 Ω are connected in three arms, and the bridge is balanced. Find the fourth resistance.
- Formula (balance condition): P/Q = R/S, i.e., 4/6 = 8/S
- Calculation: S = (6 × 8)/4 = 12 Ω
- Final Answer: S = 12 Ω
Important Formulas: V = IR, R = ρl/A, series R = R₁+R₂+…, parallel 1/R = 1/R₁+1/R₂+…, Power P = VI = I²R = V²/R, EMF equation ε = I(R + r).
Moving Charges and Magnetism – Important Questions
Conceptual Questions
- Why does a charged particle moving parallel to a magnetic field experience no force?
Because the magnetic force F = qv × B depends on the sine of the angle between v and B; when they’re parallel, sinθ = 0. - Why is a moving coil galvanometer more sensitive when it has more turns?
Because the torque on the coil (and hence the deflection) is directly proportional to the number of turns N for a given current. - State the Biot-Savart law and mention how it differs in application from Ampere’s circuital law.
Biot-Savart law gives the magnetic field due to a small current element and is used for any current geometry; Ampere’s law is more convenient when the current distribution has high symmetry.
Numerical Questions
Q1. A straight wire carrying a current of 5 A produces a magnetic field at a point 10 cm away. Find the magnetic field strength.
- Given: I = 5 A, r = 0.1 m, μ₀ = 4π × 10⁻⁷ T·m/A
- Formula: B = μ₀I / (2πr)
- Calculation: B = (4π × 10⁻⁷ × 5) / (2π × 0.1) = (2 × 10⁻⁷ × 5)/0.1
- Final Answer: B = 1 × 10⁻⁵ T
Q2. An electron moves with a velocity of 2 × 10⁶ m/s perpendicular to a magnetic field of 0.5 T. Find the force on it.
- Formula: F = qvB sinθ, θ = 90°
- Calculation: F = 1.6 × 10⁻¹⁹ × 2 × 10⁶ × 0.5
- Final Answer: F = 1.6 × 10⁻¹³ N
Important Formulas: F = qvB sinθ, F = BIL sinθ, B (straight wire) = μ₀I/2πr, B (centre of loop) = μ₀I/2R, torque on a current loop τ = NIAB sinθ.
Magnetism and Matter – Important Questions
Keep this chapter concise but don’t skip it – it’s conceptually easy marks.
- Why does a bar magnet align itself along the north-south direction when suspended freely?
Because it experiences a torque due to Earth’s magnetic field that aligns its magnetic moment with the field direction. - What is magnetic susceptibility, and how does it differ for diamagnetic, paramagnetic, and ferromagnetic materials?
It’s the ratio of magnetisation to the applied magnetic field intensity (M/H); it’s small and negative for diamagnetic materials, small and positive for paramagnetic materials, and large and positive for ferromagnetic materials. - Numerical: A bar magnet of magnetic moment 2 A·m² is placed in a uniform field of 0.2 T at 30° to the field. Find the torque on it.
- Formula: τ = MB sinθ = 2 × 0.2 × sin30° = 2 × 0.2 × 0.5
- Final Answer: τ = 0.2 N·m
Important Formulas: τ = M × B, Magnetic moment of a current loop M = NIA, Susceptibility χ = M/H, Relative permeability μᵣ = 1 + χ.
Electromagnetic Induction – Important Questions
Conceptual Questions
- State Lenz’s law and explain how it relates to the conservation of energy.
The induced current always opposes the change in magnetic flux that produced it; this is a direct consequence of energy conservation, since a current in the same direction as the change would create energy from nothing. - Why does an aluminium ring jump up when a current is switched on in a nearby coil?
The sudden increase in flux induces an opposing current in the ring (Lenz’s law), producing a repulsive force between the coil and the ring. - What determines the direction of induced EMF in a rod moving through a magnetic field?
The direction is found using the right-hand rule (or Fleming’s right-hand rule), based on the directions of velocity and magnetic field.
Numerical Questions
Q1. A coil of 100 turns and area 0.02 m² is placed in a magnetic field that changes from 0.1 T to 0.5 T in 2 seconds. Find the induced EMF.
- Formula: ε = N(ΔΦ/Δt) = N × A × (ΔB/Δt)
- Calculation: ε = 100 × 0.02 × (0.5 − 0.1)/2 = 100 × 0.02 × 0.2
- Final Answer: ε = 0.4 V
Important Formulas: Φ = BA cosθ, ε = −N(dΦ/dt), Motional EMF = Bvl, Self-inductance ε = −L(dI/dt), Mutual inductance ε₂ = −M(dI₁/dt).
Alternating Current – Important Questions
This chapter has strong problem-solving weight, so give it extra numerical practice.
Conceptual Questions
- Why is the average value of AC over a complete cycle zero, but the RMS value is not?
The positive and negative halves cancel out over a full cycle, but RMS involves squaring the values first, so the negative parts also contribute positively to the average. - What is resonance in an LCR circuit, and when does it occur?
Resonance occurs when inductive reactance equals capacitive reactance (X_L = X_C), making the impedance purely resistive and the current maximum. - Why is a transformer used only for AC and not DC? A transformer works on mutual induction, which needs a changing flux; DC produces a constant flux, so no EMF is induced in the secondary coil.
Numerical Questions
Q1. An AC source of peak voltage 220 V is connected to a circuit. Find its RMS value.
- Formula: V_rms = V₀/√2
- Calculation: V_rms = 220/1.414
- Final Answer: V_rms ≈ 155.6 V
Q2. In a series LCR circuit, X_L = 30 Ω, X_C = 10 Ω, and R = 20 Ω. Find the impedance.
- Formula: Z = √[R² + (X_L − X_C)²]
- Calculation: Z = √[20² + (30−10)²] = √[400 + 400] = √800
- Final Answer: Z ≈ 28.3 Ω
Important Formulas: V_rms = V₀/√2, I_rms = I₀/√2, X_L = ωL, X_C = 1/ωC, Z = √[R²+(X_L−X_C)²], Resonant frequency ω₀ = 1/√(LC), Power P = V_rms I_rms cosφ.
Electromagnetic Waves – Important Questions
Keep this short, a couple of definition-based questions cover most of the exam weight here.
- What is displacement current, and why was it introduced by Maxwell?
It’s a current-like term (ε₀ dΦ_E/dt) that Maxwell added to Ampere’s law to make it consistent with the continuity equation, especially in situations with a changing electric field, like a charging capacitor. - Arrange the electromagnetic spectrum in increasing order of frequency and give one use of X-rays and microwaves.
Radio waves < microwaves < infrared < visible light < ultraviolet < X-rays < gamma rays. Microwaves are used in radar and communication; X-rays are used in medical imaging. - Why do electromagnetic waves not require a medium to travel?
Because they consist of oscillating electric and magnetic fields that regenerate each other, unlike mechanical waves that need particles of a medium to propagate.
Important Formulas: c = 1/√(μ₀ε₀), c = E₀/B₀, energy density of EM wave.
Ray Optics and Optical Instruments – Important Questions
This is one of the biggest scoring chapters, so give it proper time.
Conceptual Questions
- Why does a convex lens act as a converging lens while a concave lens diverges light?
A convex lens is thicker at the centre, bending light rays inward due to progressively increasing refraction toward the edges; a concave lens is thinner at the centre and does the opposite. - What is total internal reflection, and state the two conditions required for it.
It’s the complete reflection of light back into a denser medium at the boundary with a rarer medium. Conditions: (1) light must travel from a denser to a rarer medium, (2) the angle of incidence must exceed the critical angle. - Why does a microscope use two convex lenses instead of one?
Using two lenses (objective and eyepiece) allows two-stage magnification, giving much higher overall magnifying power than a single lens.
Numerical Questions
Q1. An object is placed 20 cm from a convex lens of focal length 10 cm. Find the image distance and magnification.
- Given: u = −20 cm, f = +10 cm
- Formula: 1/v − 1/u = 1/f
- Calculation: 1/v = 1/f + 1/u = 1/10 + (−1/20) = 1/20, so v = 20 cm
- Magnification m = v/u = 20/(−20) = −1
- Final Answer: Image is formed 20 cm on the other side, real, inverted, same size (m = −1)
Q2. Light travelling from water (n = 1.33) into air strikes the surface at an angle greater than the critical angle. Find the critical angle.
- Formula: sin C = 1/n = 1/1.33
- Calculation: sin C = 0.75
- Final Answer: C ≈ 48.6°
Important Formulas: Mirror formula 1/v + 1/u = 1/f, Lens formula 1/v − 1/u = 1/f, Lens maker’s formula, Refractive index n = sin i/sin r, Power of lens P = 1/f (in metres), Magnifying power of a microscope and telescope.
Wave Optics – Important Questions
Conceptual Questions
- State Huygens’ principle. Every point on a wavefront acts as a source of secondary wavelets, and the new wavefront is the envelope of these wavelets at a later instant.
- Why do we get a bright central fringe in Young’s double-slit experiment? At the centre, the path difference from both slits is zero, so the waves arrive in phase and interfere constructively.
- How does diffraction differ from interference? Interference occurs due to superposition of waves from two (or more) coherent sources, while diffraction occurs due to the bending of waves from different parts of the same wavefront around obstacles or through a single slit.
Numerical Questions
Q1. In Young’s double-slit experiment, the slit separation is 0.5 mm, the screen is 1 m away, and the fringe width is observed to be 1.2 mm. Find the wavelength of light used.
- Formula: β = λD/d
- Calculation: λ = βd/D = (1.2 × 10⁻³ × 0.5 × 10⁻³) / 1
- Final Answer: λ = 6 × 10⁻⁷ m = 600 nm
Important Formulas: Fringe width β = λD/d, Path difference for constructive interference = nλ, for destructive interference = (n+½)λ, Brewster’s angle tan θ_B = n.
Dual Nature of Radiation and Matter – Important Questions
Conceptual Questions
- Why does the photoelectric effect support the particle nature of light?
Because emission of electrons happens instantaneously above a threshold frequency (regardless of intensity), which can only be explained if light behaves as discrete packets of energy (photons), not continuous waves. - What is the significance of work function in the photoelectric effect?
It’s the minimum energy needed to eject an electron from a metal surface; if photon energy is less than the work function, no photoelectrons are emitted, no matter how intense the light. - Why does increasing the intensity of light not increase the kinetic energy of emitted photoelectrons?
Because kinetic energy depends only on photon energy (frequency), while intensity affects only the number of photons (and hence the number of photoelectrons), as per Einstein’s photoelectric equation.
Numerical Questions
Q1. The work function of a metal is 2 eV. Find the threshold frequency.
- Formula: W₀ = hν₀
- Calculation: ν₀ = W₀/h = (2 × 1.6 × 10⁻¹⁹) / (6.63 × 10⁻³⁴)
- Final Answer: ν₀ ≈ 4.83 × 10¹⁴ Hz
Q2. Find the de Broglie wavelength of an electron accelerated through a potential difference of 100 V.
- Formula: λ = h/√(2meV)
- Calculation: λ = 6.63 × 10⁻³⁴ / √(2 × 9.1 × 10⁻³¹ × 1.6 × 10⁻¹⁹ × 100)
- Final Answer: λ ≈ 1.23 × 10⁻¹⁰ m (1.23 Å)
Important Formulas: Einstein’s photoelectric equation KE_max = hν − W₀, de Broglie wavelength λ = h/p = h/mv, Stopping potential eV₀ = hν − W₀.
Atoms – Important Questions
Conceptual Questions
- What was the major limitation of Rutherford’s atomic model?
It couldn’t explain why electrons orbiting the nucleus don’t spiral inward and collapse due to continuous emission of radiation, as predicted by classical electromagnetism. - State Bohr’s postulate about the stability of electron orbits.
Electrons can revolve only in certain fixed orbits (stationary states) where their angular momentum is an integral multiple of h/2π, and while in these orbits they do not radiate energy. - Why does the hydrogen spectrum consist of distinct lines rather than a continuous band?
Because electrons can only jump between fixed, quantised energy levels, so only specific photon energies (and hence specific wavelengths) are emitted or absorbed.
Numerical Questions
Q1. Find the radius of the first Bohr orbit of hydrogen (n = 1).
- Formula: r_n = (0.529 × n²) Å
- Calculation: r₁ = 0.529 × 1²
- Final Answer: r₁ = 0.529 Å
Q2. Calculate the energy released when an electron in a hydrogen atom jumps from n = 3 to n = 2.
- Formula: E_n = −13.6/n² eV
- Calculation: E₃ = −13.6/9 = −1.51 eV, E₂ = −13.6/4 = −3.4 eV
- ΔE = E₂ − E₃ = −3.4 − (−1.51) = −1.89 eV
- Final Answer: Energy released = 1.89 eV (this corresponds to a line in the Balmer series)
Important Formulas: r_n = n²h²ε₀/πme², E_n = −13.6/n² eV, Rydberg formula 1/λ = R(1/n₁² − 1/n₂²).
Nuclei – Important Questions
Give priority to numericals here — mass defect, binding energy, and radioactive decay questions appear almost every year.
Conceptual Questions
- What is mass defect, and why does it occur?
It’s the difference between the sum of masses of individual nucleons and the actual mass of the nucleus; it occurs because some mass is converted into binding energy that holds the nucleus together (per E = mc²). - Why is binding energy per nucleon important in explaining nuclear fission and fusion?
Nuclei near iron (mass number ~56) have the highest binding energy per nucleon; fission of heavy nuclei and fusion of light nuclei both move toward this more stable region, releasing energy. - What is half-life, and how is it different from mean life?
Half-life is the time in which half the radioactive nuclei decay; mean life is the average lifetime of a nucleus before decay and is about 1.44 times the half-life.
Numerical Questions
Q1. Calculate the binding energy of a nucleus with mass defect 0.03 u. (1 u = 931.5 MeV)
- Formula: BE = Δm × 931.5 MeV
- Calculation: BE = 0.03 × 931.5
- Final Answer: BE ≈ 27.9 MeV
Q2. A radioactive sample has a half-life of 20 days. How much of a 100 g sample remains after 60 days?
- Concept: 60 days = 3 half-lives
- Calculation: Remaining = 100 × (1/2)³ = 100/8
- Final Answer: 12.5 g remains
Important Formulas: BE = Δm c² (in MeV, use 931.5 MeV/u), N = N₀e^(−λt), Half-life T½ = 0.693/λ, Activity A = λN.
Semiconductor Electronics – Important Questions
Conceptual Questions
- What is the difference between an intrinsic and an extrinsic semiconductor?
An intrinsic semiconductor is pure, with equal numbers of electrons and holes; an extrinsic semiconductor is doped with impurities to increase either electrons (n-type) or holes (p-type). - How does a p-n junction diode allow current in only one direction?
In forward bias, the depletion region narrows, allowing majority carriers to flow easily; in reverse bias, the depletion region widens, blocking current flow (except a tiny reverse saturation current). - What is the function of a Zener diode in voltage regulation?
A Zener diode is designed to operate in reverse breakdown at a fixed voltage, so it maintains a constant output voltage across a load even when the input voltage or load current varies.
Diagram/Truth-Table Based
- Draw the circuit for a full-wave rectifier using a centre-tapped transformer and explain its working. During each half-cycle, one diode conducts while the other is reverse biased, so current flows through the load in the same direction for both half-cycles, giving a pulsating unidirectional output.
- Write the truth table for an AND gate and an OR gate. AND gate output is 1 only when both inputs are 1; OR gate output is 1 when at least one input is 1.
Important Formulas: Diode equation basics, ripple factor, gain of a transistor in CE mode, logic gate truth tables (AND, OR, NOT, NAND, NOR).
Class 12 Physics Most Important Numerical Questions
Here’s a focused set of extra numericals from the most calculation-heavy chapters, presented in the same Given → Formula → Calculation → Answer format so you can practise the method, not just the answer.
Current Electricity Two resistors of 4 Ω and 6 Ω are connected in parallel. Find the equivalent resistance. Formula: 1/R = 1/4 + 1/6 = 5/12 → R = 12/5 = 2.4 Ω
Electrostatics Find the potential at a point 5 cm from a charge of 4 μC. Formula: V = kq/r = (9×10⁹ × 4×10⁻⁶)/0.05 → V = 7.2 × 10⁵ V
Moving Charges and Magnetism A circular coil of radius 5 cm with 50 turns carries a current of 2 A. Find the magnetic field at its centre. Formula: B = μ₀NI/2R = (4π×10⁻⁷ × 50 × 2)/(2 × 0.05) → B ≈ 1.26 × 10⁻³ T
Electromagnetic Induction A rod of length 1 m moves with a velocity of 5 m/s perpendicular to a magnetic field of 0.4 T. Find the motional EMF. Formula: ε = Bvl = 0.4 × 5 × 1 → ε = 2 V
Alternating Current A pure inductor of 2 H is connected to a 50 Hz AC supply. Find its reactance. Formula: X_L = 2πfL = 2π × 50 × 2 → X_L ≈ 628 Ω
Ray Optics A concave mirror has a focal length of 15 cm. An object is placed 30 cm in front of it. Find the image position. Formula: 1/v + 1/u = 1/f → 1/v = 1/(−15) − 1/(−30) = −1/30 → v = −30 cm (real image, at the centre of curvature)
Wave Optics Two coherent sources with a path difference of 3λ/2 produce interference. What kind of fringe forms at that point? Since path difference is an odd multiple of λ/2, this gives destructive interference (a dark fringe).
Modern Physics (Dual Nature) Light of frequency 8 × 10¹⁴ Hz falls on a metal with work function 1.5 eV. Find the maximum kinetic energy of the emitted electron. Formula: KE = hν − W₀ = (6.63×10⁻³⁴ × 8×10¹⁴)/1.6×10⁻¹⁹ − 1.5 ≈ 3.32 − 1.5 → KE ≈ 1.82 eV
Nuclei A radioactive substance has decay constant λ = 0.0231 per day. Find its half-life. Formula: T½ = 0.693/λ = 0.693/0.0231 → T½ ≈ 30 days
Class 12 Physics Important Derivations
A quick, exam-ready checklist of the derivations most likely to appear as 3–5 mark questions. Revise these until you can reproduce them without looking, but don’t try to memorise word-for-word textbook language — understand the logic instead.
| Derivation | Chapter | What to Derive | Final Result |
|---|---|---|---|
| Electric field due to a dipole (axial line) | Electric Charges and Fields | Field at a point on the axis of a short dipole | E = 2kp/r³ |
| Electric field due to an infinite plane sheet | Electric Charges and Fields | Field using Gauss’s law | E = σ/2ε₀ |
| Energy stored in a charged capacitor | Electrostatic Potential and Capacitance | Work done in charging a capacitor | U = ½QV = ½CV² |
| Drift velocity and relation to current | Current Electricity | Relation between current and drift velocity of electrons | I = neAv_d |
| Force between two parallel current-carrying wires | Moving Charges and Magnetism | Force per unit length | F/l = μ₀I₁I₂/2πd |
| Torque on a current loop in a magnetic field | Moving Charges and Magnetism | Torque expression for a rectangular loop | τ = NIAB sinθ |
| Motional EMF | Electromagnetic Induction | EMF induced in a rod moving in a magnetic field | ε = Bvl |
| Self-inductance of a long solenoid | Electromagnetic Induction | L in terms of turns, area, length | L = μ₀N²A/l |
| Impedance of a series LCR circuit | Alternating Current | Relation between Z, R, X_L, X_C | Z = √[R² + (X_L − X_C)²] |
| Lens maker’s formula | Ray Optics | Relation between f, R₁, R₂, and refractive index | 1/f = (n−1)(1/R₁ − 1/R₂) |
| Fringe width in YDSE | Wave Optics | Expression for fringe spacing | β = λD/d |
| Bohr’s radius of nth orbit | Atoms | Radius in terms of n, h, m, e | r_n = n²h²ε₀/πme² |
| Einstein’s photoelectric equation | Dual Nature of Radiation and Matter | Relation between photon energy, work function, and KE | KE_max = hν − W₀ |
| Radioactive decay law | Nuclei | Relation between N, N₀, λ, t | N = N₀e^(−λt) |
Important condition to remember: most derivations assume ideal conditions — vacuum or air as medium (unless stated), point charges, thin lenses, and non-relativistic speeds. Always check whether the question changes any of these assumptions before applying a memorised result.
Class 12 Physics Important Questions for Board Exam
Knowing the right questions isn’t enough; you also need to attempt them in the format the board actually asks for. Based on the typical CBSE pattern, divide your practice into these categories:
- 1-mark / MCQ / conceptual questions – quick recall and application-based; practise these for speed and accuracy, not depth.
- Short-answer questions (2–3 marks) – usually a definition plus a brief explanation, or a small numerical.
- Numerical questions – always show units, formula, substitution, and a boxed final answer; partial marks are given for correct method even if the final number is wrong.
- Long-answer / derivation questions (5 marks) – these need a clear diagram (where applicable), labelled steps, and the final expression clearly written out.
- Case-study / source-based questions – read the passage carefully; the answers are usually hidden in the given data, so avoid over-thinking and stick to what’s asked.
Important note: exact weightage, question count, and marking scheme can shift slightly each year. Always cross-check the latest pattern against the official CBSE syllabus and sample paper for the current academic session before finalising your preparation strategy.
Class 12 Physics Important Questions PDF
[Download Class 12 Physics Important Questions PDF]
The downloadable version is meant to be a genuinely useful revision tool, not just a copy of this page. It should include:
- Chapter-wise important questions
- The most important numerical questions
- Complete answers and step-by-step solutions
- All key formulas, organised chapter-wise
- The important derivations table
- A blank checklist so students can tick off chapters as they revise
Download the Class 12 Physics Important Questions PDF and use it for chapter-wise revision and quick practice before your exam.
How to Use These Class 12 Physics Important Questions
Don’t just read through this list, use it properly:
- Revise the chapter concept first. Go through your notes or NCERT for that chapter before attempting the questions.
- Attempt the questions without looking at the solution. This is where the real learning happens; give yourself a genuine shot before checking the answer.
- Analyse your mistakes. If you got a numerical wrong, figure out whether it was a concept gap, a formula mix-up, or a calculation slip; these need different fixes.
- Re-attempt the questions you got wrong, after a gap of a few days. This is what actually moves a topic from “seen once” to “exam-ready.”
A quick note on how to use this differently, depending on your goal:
- For board exams: focus on presentation, clear diagrams, properly labelled derivations, and step-wise numerical solutions, since marks are often given for the method.
- For JEE/NEET preparation: use these questions mainly for concept revision, but don’t stop here; continue with subject-specific PYQs and higher-difficulty problem sets, since competitive exams test application at a different level.
Frequently Asked Questions
What are the most important chapters in Class 12 Physics?
Current Electricity, Ray Optics, Electromagnetic Induction, Moving Charges and Magnetism, and Nuclei are generally considered high-weightage chapters because they combine strong conceptual and numerical value. That said, don’t skip the smaller chapters like Electromagnetic Waves or Magnetism and Matter — they’re quick to revise and often carry easy, guaranteed marks.
Where can I find Class 12 Physics important questions with solutions?
This page covers chapter-wise important questions with step-by-step solutions for every unit in the Class 12 Physics syllabus. You can also download the complete PDF above for offline revision.
How should I prepare Class 12 Physics for the board exam?
Start with NCERT to build your concepts, then move on to important questions and previous year papers for practice. Focus on writing full, labelled solutions for numericals and derivations, since the CBSE marking scheme rewards correct method and presentation, not just the final answer.
How many Physics questions should I practise every day?
This depends on how much time you have left before your exam. If you’re preparing over several months, 8–10 focused questions a day across concepts and numericals is enough to build steady progress. Closer to exams, with limited time, it’s better to prioritise high-weightage chapters and previous year questions over sheer quantity.
Are Class 12 Physics numerical questions important?
Yes — numericals typically make up a large share of the marks in board exams and are essential for competitive exams like JEE and NEET. They also test whether you actually understand a formula, not just remember it, which is exactly what examiners are checking for.
