JIPMER Entrance Physics Flashcards

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.

1. State Faraday's laws of electromagnetic induction and Lenz's law.

   Induced EMF = -dΦ/dt (rate of change of magnetic flux); EMF magnitude proportional to rate of flux change. Lenz's law: induced current opposes the change causing it (energy conservation); the minus sign expresses this.

2. Define self-inductance and mutual inductance.

   Self-inductance L: EMF induced in a coil due to change in its own current, ε = -L dI/dt. Mutual inductance M: EMF in one coil due to changing current in a neighboring coil, ε₂ = -M dI₁/dt.

3. In AC, define rms value and give the relation to peak value; state the resonance condition for an LCR circuit.

   I_rms = I_peak/√2, V_rms = V_peak/√2. Resonance occurs when X_L = X_C, i.e. ω = 1/√(LC); impedance is minimum and current is maximum.

4. Define inductive and capacitive reactance and impedance of a series LCR circuit.

   X_L = ωL, X_C = 1/ωC. Impedance Z = √(R² + (X_L - X_C)²); power factor cosφ = R/Z.

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

   Radio < microwave < infrared < visible < ultraviolet < X-rays < gamma rays. All travel at c = 3 x 10⁸ m/s in vacuum; c = 1/√(μ₀ε₀).

6. State the laws of reflection and the mirror formula.

   Angle of incidence = angle of reflection; incident ray, reflected ray, and normal lie in one plane. Mirror formula: 1/v + 1/u = 1/f; magnification m = -v/u.

7. State Snell's law and define critical angle and total internal reflection.

   n₁ sinθ₁ = n₂ sinθ₂. Critical angle θ_c: sinθ_c = 1/n; for incidence beyond θ_c (going to a rarer medium), light undergoes total internal reflection.

8. Give the lens maker's formula and the formula for power of a lens.

   Lens maker's: 1/f = (n-1)(1/R₁ - 1/R₂). Lens formula: 1/v - 1/u = 1/f. Power P = 1/f (in metres), unit dioptre (D); powers add for lenses in contact.

9. State the condition for fringe formation in Young's double-slit experiment and the fringe width.

   Bright fringes: path difference = nλ; dark fringes: (n+½)λ. Fringe width β = λD/d, where D is slit-to-screen distance and d is slit separation.

10. What is the difference between interference and diffraction?

    Interference: superposition of waves from two (or more) coherent sources, giving equally spaced fringes of uniform intensity. Diffraction: bending of light around an obstacle/slit from secondary wavelets of a single source, giving unequal fringes with a bright central maximum.

11. Define polarization and state Brewster's law.

    Polarization restricts light vibrations to one plane, proving light is transverse. Brewster's law: tan i_p = n, where i_p is the polarizing angle; reflected and refracted rays are perpendicular at this angle.

12. State Einstein's photoelectric equation and define work function.

    KE_max = hf - φ₀, where φ₀ is the work function (minimum energy to eject an electron). Stopping potential V₀: eV₀ = hf - φ₀; threshold frequency f₀ = φ₀/h.

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

    Matter has wave nature; a particle of momentum p has wavelength λ = h/p = h/mv. For an electron accelerated through V: λ = 12.27/√V Å.

14. State the key observations of the photoelectric effect that classical physics could not explain.

    Emission is instantaneous; max KE depends on frequency not intensity; below threshold frequency no emission occurs regardless of intensity; current (number of electrons) depends on intensity.

15. State Bohr's postulates for the hydrogen atom.

    Electrons orbit in stationary states without radiating; angular momentum is quantized, L = nh/2π; energy is emitted/absorbed only when an electron jumps between orbits, hf = E_2 - E_1.

16. Give the energy of the nth Bohr orbit of hydrogen and the radius of the first orbit.

    E_n = -13.6/n² eV (ground state -13.6 eV). Radius r_n = 0.529 n² Å; first Bohr radius = 0.529 Å. Energy increases (less negative) with n.

17. Write the Rydberg formula for the hydrogen spectrum and name the visible series.

    1/λ = R(1/n₁² - 1/n₂²), R = 1.097 x 10⁷ m⁻¹. The Balmer series (transitions to n=2) lies in the visible region; Lyman (n=1) is UV, Paschen (n=3) is IR.

18. Define mass defect and binding energy of a nucleus.

    Mass defect Δm = (sum of nucleon masses) - (actual nuclear mass). Binding energy = Δm·c² (1 u = 931.5 MeV); higher binding energy per nucleon means a more stable nucleus (peak near iron).

19. Compare alpha, beta, and gamma radiation.

    Alpha: helium nucleus (²₄He), +2 charge, least penetrating, most ionizing. Beta: electron/positron, -1/+1 charge, moderate penetration. Gamma: high-energy photon, no charge, most penetrating, least ionizing.

20. State the law of radioactive decay and define half-life.

    N = N₀e^(-λt); activity ∝ number of nuclei. Half-life T½ = ln2/λ = 0.693/λ is the time for half the nuclei to decay; mean life τ = 1/λ = T½/0.693.

21. Distinguish nuclear fission from nuclear fusion.

    Fission: a heavy nucleus splits into lighter nuclei releasing energy (e.g. U-235 in reactors). Fusion: light nuclei combine into a heavier nucleus releasing energy (e.g. in the Sun); fusion releases more energy per nucleon.

22. Distinguish intrinsic from extrinsic semiconductors and define n-type and p-type doping.

    Intrinsic: pure semiconductor (Si, Ge) with equal electrons and holes. Extrinsic: doped. n-type: doped with pentavalent (donor) impurity, electrons majority carriers. p-type: doped with trivalent (acceptor) impurity, holes majority carriers.

23. Explain the working of a p-n junction diode under forward and reverse bias.

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

24. What is a rectifier, and how does a full-wave rectifier differ from a half-wave rectifier?

    A rectifier converts AC to DC using diodes. Half-wave uses one diode and conducts for half the cycle; full-wave (two diodes or bridge of four) conducts both halves, giving higher efficiency and lower ripple.

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