VITEEE 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. For an AC circuit, give the rms value of current and the inductive and capacitive reactances.

   I_rms = I₀/√2 (and V_rms = V₀/√2). Inductive reactance X_L = ωL = 2πfL. Capacitive reactance X_C = 1/(ωC) = 1/(2πfC).

2. Give the impedance and resonance condition of a series LCR circuit.

   Impedance Z = √(R² + (X_L − X_C)²). At resonance X_L = X_C, so Z = R (minimum), current is maximum, and the resonant frequency is f₀ = 1/(2π√(LC)).

3. State the displacement current concept and the speed of electromagnetic waves.

   Maxwell introduced displacement current I_d = ε₀(dΦ_E/dt) to account for changing electric fields producing magnetic fields. EM waves travel at c = 1/√(μ₀ε₀) ≈ 3×10⁸ m/s in vacuum, with E and B perpendicular to each other and to propagation.

4. List the electromagnetic spectrum in order of increasing frequency (decreasing wavelength).

   Radio waves → microwaves → infrared → visible light → ultraviolet → X-rays → gamma rays (increasing frequency and energy, decreasing wavelength).

5. State the mirror formula and the lens-maker's formula.

   Mirror formula: 1/v + 1/u = 1/f. Lens-maker's formula: 1/f = (n − 1)(1/R₁ − 1/R₂), where n is the refractive index relative to the surroundings. (Lens equation: 1/v − 1/u = 1/f.)

6. State Snell's law and define total internal reflection with its conditions.

   Snell's law: n₁ sinθ₁ = n₂ sinθ₂. Total internal reflection occurs when light travels from a denser to a rarer medium and the angle of incidence exceeds the critical angle θ_c, where sinθ_c = n₂/n₁ (n₂ < n₁).

7. Define magnifying power of a compound microscope and an astronomical telescope (normal adjustment).

   Compound microscope: M = (L/f_o)(D/f_e), where D = 25 cm (least distance of distinct vision). Telescope (normal adjustment): M = f_o/f_e, with tube length = f_o + f_e.

8. State Huygens' principle.

   Every point on a wavefront acts as a source of secondary spherical wavelets that spread out in the forward direction at the wave's speed; the new wavefront is the forward envelope (tangent surface) of these secondary wavelets.

9. Give the conditions for constructive and destructive interference and the fringe width in Young's double-slit experiment.

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

10. For single-slit diffraction, give the condition for minima; and state what polarization demonstrates.

    Single-slit minima occur at a sinθ = nλ (n = 1, 2, 3…), where a is slit width. Polarization (restriction of vibrations to one plane) demonstrates that light is a transverse wave; Brewster's law: tanθ_p = n.

11. State Einstein's photoelectric equation and define work function and threshold frequency.

    Einstein's equation: hf = φ + KE_max, i.e. KE_max = hf − φ. Work function φ is the minimum energy to eject an electron. Threshold frequency f₀ = φ/h is the minimum frequency below which no emission occurs regardless of intensity.

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

    De Broglie proposed that 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 (≈ h/√(2mqV)).

13. State the postulates of Bohr's model of the hydrogen atom.

    1) Electrons revolve in certain stable orbits without radiating. 2) Angular momentum is quantized: mvr = nh/2π. 3) Energy is emitted/absorbed only when an electron jumps between orbits, with hf = E₂ − E₁.

14. Give the energy of the nth level of hydrogen and the Rydberg formula for spectral lines.

    Energy: E_n = −13.6/n² eV (ground state −13.6 eV). Rydberg formula: 1/λ = R(1/n₁² − 1/n₂²), where R = 1.097×10⁷ m⁻¹ (Lyman, Balmer, Paschen series for n₁ = 1, 2, 3).

15. Define mass defect, binding energy, and explain nuclear stability via binding energy per nucleon.

    Mass defect Δm = (sum of nucleon masses) − (actual nuclear mass). Binding energy = Δm·c² (E = mc²). Binding energy per nucleon peaks (~8.8 MeV) near iron (A ≈ 56); higher BE/nucleon means greater stability.

16. Distinguish nuclear fission and fusion and define the law of radioactive decay.

    Fission: a heavy nucleus splits into lighter nuclei, releasing energy (e.g. U-235). Fusion: light nuclei combine into a heavier nucleus, releasing energy (e.g. in stars). Radioactive decay law: N = N₀e^(−λt); half-life T½ = 0.693/λ.

17. Distinguish conductors, insulators, and semiconductors by their energy band gaps.

    Conductors: conduction and valence bands overlap (no gap). Insulators: large band gap (E_g > 3 eV). Semiconductors: small band gap (~1 eV, e.g. Si 1.1 eV, Ge 0.7 eV) so conductivity increases with temperature.

18. Differentiate intrinsic, n-type, and p-type semiconductors.

    Intrinsic: pure semiconductor, electrons = holes. n-type: doped with pentavalent (donor) impurity, majority carriers are electrons. p-type: doped with trivalent (acceptor) impurity, majority carriers are holes. The crystal remains electrically neutral.

19. Explain forward and reverse bias of a p-n junction diode.

    Forward bias: p-side connected to positive terminal; depletion layer narrows, barrier lowers, large current flows. Reverse bias: p-side to negative; depletion layer widens, only tiny saturation current flows. The diode thus conducts mainly in one direction.

20. Compare half-wave and full-wave rectification.

    A rectifier converts AC to DC. Half-wave (one diode) conducts during one half-cycle only — output efficiency ~40.6%. Full-wave (two diodes/centre tap or bridge of four diodes) uses both half-cycles — efficiency ~81.2% with smoother, higher-frequency ripple.

21. State the truth tables (outputs) of basic logic gates AND, OR, and NOT.

    AND: output 1 only when all inputs are 1 (Y = A·B). OR: output 1 when any input is 1 (Y = A+B). NOT: output is the inverse of input (Y = Ā). NAND and NOR are universal gates.

22. List the basic elements of a communication system.

    Transmitter (encodes/modulates the signal), communication channel/medium (carries the signal, may add noise), and receiver (detects/demodulates and recovers the message). Key sub-blocks include transducer, modulator, repeater, amplifier, and demodulator.

23. Define modulation and name its three main types for analog signals.

    Modulation is superimposing a low-frequency message signal onto a high-frequency carrier wave for transmission. The three types are amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM) — varying the carrier's amplitude, frequency, or phase respectively.

24. Distinguish ground wave, sky wave, and space wave propagation.

    Ground wave: travels along Earth's surface, used for low/medium frequencies (up to ~2 MHz). Sky wave: reflected by the ionosphere, used for short-wave (HF, 3–30 MHz) long-distance. Space wave: line-of-sight propagation for VHF/UHF and microwaves (TV, satellite).

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