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COMEDK UGET Physics - Electromagnetism and Modern Physics Flashcards
61 question-and-answer cards covering Physics - Electromagnetism and Modern Physics as it is examined in COMEDK UGET. 24 of them are printed below, taken from across the deck — no signup, no paywall on the preview.
24 sample cards from the Physics - Electromagnetism and Modern Physics deck
Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.
Define inductive and capacitive reactance in AC circuits.
Inductive reactance X_L = ωL = 2πfL (increases with frequency). Capacitive reactance X_C = 1/(ωC) = 1/(2πfC) (decreases with frequency). Both measured in ohms.
Give the impedance of a series LCR circuit and the resonance frequency.
Impedance Z = √[R² + (X_L - X_C)²]. Resonance occurs when X_L = X_C, giving f₀ = 1/(2π√(LC)), where Z is minimum (= R) and current is maximum.
Define power factor in an AC circuit.
Power factor = cosφ = R/Z, where φ is the phase angle between voltage and current. Average power P = V_rms·I_rms·cosφ. For a pure inductor or capacitor, cosφ = 0 (wattless current).
State the principle of a transformer and the turns ratio relation.
A transformer works on mutual induction, transferring AC power between coils. V_s/V_p = N_s/N_p = I_p/I_s. Step-up: N_s > N_p (increases voltage); step-down: N_s < N_p.
Give the order of frequency/wavelength of the electromagnetic spectrum from low to high frequency.
Increasing frequency (decreasing wavelength): radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays.
What is the speed of electromagnetic waves in vacuum and its relation to ε₀ and μ₀?
c = 1/√(μ₀ε₀) ≈ 3 × 10⁸ m/s. EM waves are transverse, with E and B perpendicular to each other and to the direction of propagation, and E₀/B₀ = c.
State the laws of reflection and the mirror formula.
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.
State Snell's law of refraction and define refractive index.
Snell's law: n₁ sinθ₁ = n₂ sinθ₂. Refractive index n = c/v = sin(i)/sin(r), the ratio of speed of light in vacuum to that in the medium.
Define critical angle and the condition for total internal reflection.
Critical angle C is the angle of incidence in the denser medium for which the refraction angle is 90°: sin C = 1/n. Total internal reflection occurs when light travels from denser to rarer medium and the angle of incidence exceeds C.
Give the lens maker's formula and the lens formula.
Lens maker's formula: 1/f = (n-1)(1/R₁ - 1/R₂). Lens formula: 1/v - 1/u = 1/f. Power P = 1/f (in metres), measured in dioptres (D). Magnification m = v/u.
State Huygens' principle and the conditions for constructive/destructive interference.
Huygens' principle: every point on a wavefront acts as a source of secondary wavelets; the new wavefront is their envelope. Constructive interference: path difference = nλ. Destructive: path difference = (n + ½)λ.
Give the fringe width formula in Young's double-slit experiment.
Fringe width β = λD/d, where λ is wavelength, D the slit-to-screen distance, and d the slit separation. Bright fringes at path difference nλ; dark at (n + ½)λ.
What is dispersion of light and what causes it? Give the order of the spectrum.
Dispersion is the splitting of white light into its constituent colors by a prism, caused because refractive index depends on wavelength (violet bends most, red least). The spectrum order is VIBGYOR: violet, indigo, blue, green, yellow, orange, red.
State Rayleigh's law of scattering and explain why the sky is blue.
Intensity of scattered light is inversely proportional to the fourth power of wavelength: I ∝ 1/λ⁴. Blue light (shorter wavelength) scatters more than red, so the sky appears blue; the sun appears red at sunrise/sunset due to longer path scattering away the blue.
State Einstein's photoelectric equation and define work function.
KE_max = hν - φ₀, where hν is photon energy and φ₀ the work function (minimum energy to eject an electron). Threshold frequency ν₀ = φ₀/h. Stopping potential: eV₀ = KE_max.
Give the de Broglie wavelength formula for a moving particle.
λ = h/p = h/(mv) = h/√(2mKE). For an electron accelerated through potential V: λ = 12.27/√V Å. This expresses the wave nature of matter.
State Bohr's postulates for the hydrogen atom and give the energy of the nth level.
Electrons move in stationary orbits where angular momentum is quantized: mvr = nh/2π. Energy is radiated only on transition between orbits: hν = E₂ - E₁. Energy: Eₙ = -13.6/n² eV. Radius rₙ ∝ n².
What is the Rydberg formula for hydrogen spectral lines and name the series in the visible region?
1/λ = R(1/n₁² - 1/n₂²), where R = 1.097 × 10⁷ m⁻¹. The Balmer series (transitions to n = 2) lies in the visible region. Lyman series is UV; Paschen, Brackett are infrared.
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 (maximum near iron, A ≈ 56).
Compare alpha, beta, and gamma radiations.
Alpha (α): helium nucleus (²₄He), positive charge, least penetrating, most ionizing. Beta (β): electron/positron, negative/positive, moderate penetration. Gamma (γ): high-energy EM photon, no charge, most penetrating, least ionizing.
State the law of radioactive decay and define half-life.
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. Mean life τ = 1/λ. Activity A = λN.
Distinguish between nuclear fission and nuclear fusion.
Fission: a heavy nucleus splits into lighter nuclei releasing energy (e.g., U-235 in reactors/bombs). Fusion: light nuclei combine into a heavier one releasing energy (e.g., hydrogen to helium in the Sun); requires extremely high temperature.
Distinguish between intrinsic and extrinsic (n-type and p-type) semiconductors.
Intrinsic: pure semiconductor; equal electrons and holes. Extrinsic: doped. n-type doped with pentavalent impurity (electrons are majority carriers); p-type doped with trivalent impurity (holes are majority carriers).
Explain forward and reverse bias of a p-n junction diode and its use as a rectifier.
Forward bias: p connected to positive terminal; barrier reduced, large current flows. Reverse bias: p to negative; barrier increased, only tiny leakage current. A diode conducts in one direction, so it acts as a rectifier (half-wave uses one diode, full-wave uses two/four).
What this deck covers
The Physics - Electromagnetism and Modern Physics deck follows the COMEDK UGET Physics - Electromagnetism and Modern Physics syllabus — 6 chapters and 18 topics — so questions land on material that is genuinely examinable rather than trivia around it. That works out to roughly 10.2 cards per chapter.
Answers are written to be recallable, not just readable — averaging about 188 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 - Electromagnetism and Modern Physics flashcards FAQ
How many Physics - Electromagnetism and Modern Physics flashcards are in this COMEDK UGET deck?
61 cards. This page previews 24 of them, sampled evenly across the deck so you can judge the difficulty before installing anything.
Are these COMEDK UGET flashcards free?
Yes. The preview here is free to read with no signup, and the full 61-card deck is free inside the Examius app.
What do the Physics - Electromagnetism and Modern Physics cards cover?
They follow the COMEDK UGET Physics - Electromagnetism and Modern Physics syllabus — 6 chapters and 18 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.