AFMC / NEET-linked AFMC Admission Physics (NEET-UG Academic Component) Flashcards

24 sample cards from the Physics (NEET-UG Academic Component) deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. State the Doppler effect formula for sound when the source and observer move.

   f' = f·(v ± v₀)/(v ∓ v_s), where v = speed of sound, v₀ = observer speed, v_s = source speed. Use top signs for relative approach (frequency increases) and bottom signs for recession (frequency decreases).

2. State Coulomb's law and define electric field intensity.

   Coulomb's law: F = (1/4πε₀)·q₁q₂/r², with 1/4πε₀ = 9×10⁹ N·m²/C². Electric field E = F/q₀ (force per unit positive test charge); SI unit N/C or V/m; it is a vector pointing away from positive charge.

3. State Gauss's law and the field due to an infinite line charge and an infinite sheet of charge.

   Gauss's law: net flux Φ = q_enc/ε₀. Infinite line charge: E = λ/(2πε₀r). Infinite charged sheet: E = σ/(2ε₀) (independent of distance).

4. Define electric potential and capacitance, and give the capacitance of a parallel plate capacitor.

   Electric potential V = work per unit charge to bring a charge from infinity (V = W/q). Capacitance C = Q/V (unit: farad). Parallel plate capacitor: C = ε₀A/d (vacuum); with dielectric C = Kε₀A/d. Energy stored = ½CV².

5. State Ohm's law and give formulas for resistors in series and in parallel.

   Ohm's law: V = IR (at constant temperature). Series: R_eq = R₁ + R₂ + ... Parallel: 1/R_eq = 1/R₁ + 1/R₂ + ... Resistance R = ρL/A, where ρ is resistivity.

6. State Kirchhoff's two laws for circuits.

   Junction (current) rule: sum of currents entering a junction = sum leaving (conservation of charge, ΣI = 0). Loop (voltage) rule: sum of EMFs and potential drops around any closed loop = 0 (conservation of energy).

7. State the right-hand rule and Biot-Savart law for the magnetic field of a current. Give B at the center of a circular loop and inside a solenoid.

   Biot-Savart: dB = (μ₀/4π)·(I dl × r̂)/r². At the center of a circular loop of radius R: B = μ₀I/2R. Inside a long solenoid: B = μ₀nI, where n is turns per unit length.

8. State Faraday's law and Lenz's law of electromagnetic induction.

   Faraday's law: induced EMF = −dΦ/dt (rate of change of magnetic flux). For N turns, EMF = −N dΦ/dt. Lenz's law: the induced current opposes the change in flux that produces it (the negative sign), consistent with conservation of energy.

9. Define inductive and capacitive reactance, and impedance in a series LCR AC circuit. When does resonance occur?

   X_L = ωL = 2πfL; X_C = 1/ωC = 1/2πfC. Impedance Z = √(R² + (X_L − X_C)²). Resonance occurs when X_L = X_C, giving f = 1/(2π√(LC)), minimum impedance Z = R and maximum current.

10. List the electromagnetic spectrum in order of increasing frequency and give the speed of EM waves.

    Radio waves < microwaves < infrared < visible light < ultraviolet < X-rays < gamma rays (increasing frequency, decreasing wavelength). All travel at c = 3×10⁸ m/s in vacuum; c = 1/√(μ₀ε₀); E and B are perpendicular to each other and to propagation.

11. State the laws of reflection and the mirror formula with sign convention.

    Laws of reflection: angle of incidence = angle of reflection; incident ray, reflected ray, and normal lie in one plane. Mirror formula: 1/v + 1/u = 1/f, where f = R/2. Magnification m = −v/u.

12. State Snell's law of refraction and the condition for total internal reflection.

    Snell's law: n₁ sinθ₁ = n₂ sinθ₂ (n = refractive index). Total internal reflection occurs when light travels from a denser to a rarer medium at an angle greater than the critical angle θc, where sinθc = 1/n (= n_rarer/n_denser).

13. Give the lens formula, lensmaker's formula, and definition of power of a lens.

    Lens formula: 1/v − 1/u = 1/f. Lensmaker's formula: 1/f = (n−1)(1/R₁ − 1/R₂). Power P = 1/f (in meters), unit dioptre (D). For lenses in contact: P = P₁ + P₂.

14. State the conditions for sustained interference and the fringe width formula in Young's double-slit experiment.

    Conditions: the two sources must be coherent (constant phase difference) and monochromatic, with comparable amplitudes. Fringe width β = λD/d, where D = slit-to-screen distance and d = slit separation. Constructive: path difference = nλ; destructive = (n+½)λ.

15. Explain diffraction and the condition for the first minimum in single-slit diffraction.

    Diffraction is the bending of waves around obstacles/edges and spreading after passing through a slit. For single-slit, the first minimum occurs when a·sinθ = λ (a = slit width). The central maximum is the brightest and twice as wide as the others.

16. What is Brewster's law / polarization by reflection?

    When unpolarized light strikes a surface at Brewster's angle θ_p, the reflected light is completely plane-polarized. Brewster's law: tanθ_p = n (refractive index). At this angle, reflected and refracted rays are perpendicular.

17. State the photoelectric effect and Einstein's photoelectric equation.

    Photoelectric effect: emission of electrons when light of sufficient frequency hits a metal. Einstein's equation: KE_max = hf − φ₀, where φ₀ = hf₀ is the work function and f₀ the threshold frequency. Below f₀ no emission occurs regardless of intensity; KE depends on frequency, not intensity.

18. State the de Broglie hypothesis and give the de Broglie wavelength formula.

    Matter has wave nature: every moving particle has an associated wavelength λ = h/p = h/mv. For an electron accelerated through potential V: λ = 12.27/√V Å. This explains wave-particle duality.

19. State the postulates of Bohr's model and give the energy of the nth orbit in hydrogen.

    Postulates: electrons orbit in stationary states without radiating; angular momentum is quantized (mvr = nh/2π); energy is emitted/absorbed only on jumping between orbits (hf = E₂ − E₁). Energy of nth level: Eₙ = −13.6/n² eV. Ground state = −13.6 eV.

20. Define mass defect, binding energy, and explain nuclear fission vs fusion.

    Mass defect Δm = (mass of nucleons) − (mass of nucleus); binding energy = Δm·c² (energy holding the nucleus together). Fission: a heavy nucleus splits into lighter ones releasing energy. Fusion: light nuclei combine into a heavier one releasing energy. Both release energy because products have higher binding energy per nucleon.

21. State the law of radioactive decay and define half-life and the three types of radiation.

    N = N₀e^(−λt), where λ is the decay constant. Half-life T½ = 0.693/λ (time for half the nuclei to decay). Alpha (²He⁴, positive, low penetration), beta (electron, moderate penetration), gamma (high-energy EM wave, high penetration, no charge).

22. Distinguish between intrinsic and extrinsic semiconductors, and between p-type and n-type.

    Intrinsic: pure semiconductor (Si/Ge), equal electrons and holes. Extrinsic: doped semiconductor. n-type: doped with pentavalent impurity (e.g., As/P), majority carriers = electrons. p-type: doped with trivalent impurity (e.g., B/Al), majority carriers = holes.

23. Explain the behavior of a p-n junction diode in forward and reverse bias.

    Forward bias (p to +, n to −): depletion layer narrows, diode conducts, low resistance. Reverse bias (p to −, n to +): depletion layer widens, only tiny leakage current flows (high resistance). A diode acts as a one-way valve / rectifier.

24. Compare half-wave and full-wave rectifiers and name the basic logic gates.

    Half-wave rectifier uses one diode, converts only one half of the AC cycle (low efficiency). Full-wave rectifier (two diodes or a bridge of four) uses both halves (higher efficiency, ripple frequency = 2× input). Basic logic gates: OR, AND, NOT; universal gates: NAND and NOR.

What this deck covers

Physics (NEET-UG Academic Component) flashcards FAQ