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🇮🇳 ISC Class 12 · flashcards
ISC Class 12 Physics Flashcards
68 question-and-answer cards covering Physics as it is examined in ISC Class 12. 24 of them are printed below, taken from across the deck — no signup, no paywall on the preview.
24 sample cards from the Physics deck
Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.
Give one source and one use each for X-rays and microwaves.
X-rays: produced by deceleration of high-energy electrons hitting a metal target; used in medical imaging and crystallography. Microwaves: produced by klystron/magnetron tubes; used in radar and microwave ovens/communication.
State the laws of reflection of light.
(1) The angle of incidence equals the angle of reflection (i = r). (2) The incident ray, reflected ray, and normal at the point of incidence all lie in the same plane.
State Snell's law of refraction and define refractive index.
Snell's law: n₁ sin i = n₂ sin r. The refractive index of a medium n = c/v = (speed of light in vacuum)/(speed in medium), also equal to sin i/sin r when light goes from vacuum to the medium.
Define critical angle and state the condition for total internal reflection.
The critical angle θ_c is the angle of incidence in the denser medium for which the angle of refraction is 90°: sinθ_c = 1/n. Total internal reflection occurs when light travels from a denser to rarer medium and the angle of incidence exceeds θ_c.
Write the lens maker's formula and the thin lens equation.
Lens maker's formula: 1/f = (n−1)(1/R₁ − 1/R₂). Thin lens equation: 1/v − 1/u = 1/f, where u, v are object and image distances and f the focal length.
Define the magnifying power of a compound microscope.
M = m_o × m_e = (L/f_o)(D/f_e), the product of the linear magnification of the objective and the angular magnification of the eyepiece, where L is tube length, D the least distance of distinct vision (25 cm), and f_o, f_e the focal lengths.
State the conditions for constructive and destructive interference of light.
Constructive (bright fringe): path difference = nλ (n = 0,1,2,...). Destructive (dark fringe): path difference = (n + ½)λ. Sources must be coherent.
Write the fringe width formula in Young's double-slit experiment.
β = λD/d, where λ is the wavelength, D the slit-to-screen distance, and d the separation between the slits.
What is the photoelectric effect and Einstein's photoelectric equation?
The photoelectric effect is the emission of electrons from a metal surface when light of suitable frequency falls on it. Einstein's equation: hν = φ + ½mv²_max, where hν is photon energy, φ the work function, and ½mv²_max the maximum kinetic energy of emitted electrons.
Define threshold frequency and work function.
Threshold frequency ν₀ is the minimum frequency of incident light below which no photoemission occurs. Work function φ = hν₀ is the minimum energy required to eject an electron from the metal surface.
State de Broglie's hypothesis and the wavelength of a matter wave.
Every moving particle has an associated wave. The de Broglie wavelength λ = h/p = h/mv, where h is Planck's constant, p the momentum. For an electron accelerated through V volts, λ ≈ 1.227/√V nm.
State the postulates of Bohr's model of the hydrogen atom.
(1) Electrons revolve in certain stable orbits without radiating energy. (2) Angular momentum is quantised: mvr = nh/2π. (3) Energy is emitted/absorbed only when an electron jumps between orbits: hν = E₂ − E₁.
Give the energy of the nth orbit of a hydrogen atom and the ground state energy.
Eₙ = −13.6/n² eV. The ground state (n=1) energy is −13.6 eV; the negative sign indicates the electron is bound.
Define mass defect and binding energy of a nucleus.
Mass defect Δm is the difference between the sum of masses of the constituent nucleons and the actual mass of the nucleus. Binding energy = Δm·c² is the energy needed to separate the nucleus into its nucleons (energy released when it forms).
Distinguish between nuclear fission and nuclear fusion.
Fission: a heavy nucleus splits into lighter nuclei releasing energy (e.g., U-235). Fusion: light nuclei combine to form a heavier nucleus releasing energy (e.g., in the Sun). Both release energy because products have higher binding energy per nucleon.
State the law of radioactive decay and define half-life.
The rate of decay is proportional to the number of undecayed nuclei: N = N₀e^(−λt), where λ is the decay constant. Half-life T₁/₂ = 0.693/λ is the time for half the nuclei to decay.
Distinguish between intrinsic and extrinsic semiconductors.
Intrinsic: pure semiconductor (e.g., pure Si/Ge) with equal numbers of electrons and holes. Extrinsic: doped with impurities to increase conductivity — n-type (pentavalent dopant, electrons majority) or p-type (trivalent dopant, holes majority).
What is a p-n junction diode and what is depletion region?
A p-n junction is formed by joining p-type and n-type semiconductors. The depletion region is the charge-free zone near the junction where diffused electrons and holes recombine, leaving immobile ions that set up a potential barrier.
Distinguish between forward bias and reverse bias of a diode.
Forward bias: p-side connected to positive terminal; barrier decreases, large current flows. Reverse bias: p-side to negative terminal; barrier increases, only a small reverse saturation current flows. A diode conducts mainly in forward bias.
What is the function of a Zener diode?
A Zener diode operates in the reverse breakdown region at a fixed voltage and is used as a voltage regulator, maintaining a constant output voltage despite changes in input voltage or load.
Describe the three regions of a transistor and the two types.
A transistor has three regions: emitter (heavily doped), base (thin, lightly doped), and collector (moderately doped, large). The two types are NPN and PNP, based on the arrangement of doped layers.
Define the current gain α and β of a transistor in common-base and common-emitter configurations.
α = I_C/I_E (common base, slightly less than 1). β = I_C/I_B (common emitter, large, ~20–200). They relate as β = α/(1−α).
How does a transistor act as an amplifier?
In active mode (emitter-base forward biased, collector-base reverse biased), a small change in base/input current produces a large change in collector/output current. A load resistor converts this into a larger output voltage, giving voltage gain (A_V = β × R_out/R_in).
What is the principle of a transformer and the turns ratio relation?
A transformer works on mutual induction: a changing current in the primary induces an EMF in the secondary. For an ideal transformer V_s/V_p = N_s/N_p = I_p/I_s, where N is the number of turns. Step-up has N_s > N_p; step-down has N_s < N_p.
What this deck covers
The Physics deck follows the ISC Class 12 Physics syllabus — 9 chapters and 19 topics — so questions land on material that is genuinely examinable rather than trivia around it. That works out to roughly 7.6 cards per chapter.
Answers are written to be recallable, not just readable — averaging about 203 characters, which is long enough to carry the reasoning and short enough to say out loud.
A deck like this earns its keep on the second and third pass. Read the syllabus first so you know the shape of the subject, then use the cards to find the specific facts that have not stuck.
Physics flashcards FAQ
How many Physics flashcards are in this ISC Class 12 deck?
68 cards. This page previews 24 of them, sampled evenly across the deck so you can judge the difficulty before installing anything.
Are these ISC Class 12 flashcards free?
Yes. The preview here is free to read with no signup, and the full 68-card deck is free inside the Examius app.
What do the Physics cards cover?
They follow the ISC Class 12 Physics syllabus — 9 chapters and 19 topics — so the questions track what is actually examinable.
How should I use these flashcards?
Read the syllabus first so you know the shape of the subject, then drill the deck. Examius schedules each card with spaced repetition, so cards you keep missing come back sooner and ones you know drift further apart.