Chapter 1
Light: Reflection & Refraction
Mirror Formula & Magnification
(1/f) = (1/v) + (1/u) | Magnification (m) = -v / u = h_i / h_o
Concave mirror: f is negative; Convex mirror: f is positive.
Variables: f = focal length (f = R/2), u = object distance (always negative in Cartesian convention), v = image distance
Exam Tip: If m is negative, image is REAL and INVERTED. If m is positive, image is VIRTUAL and ERECT.
Lens Formula, Snell Law & Lens Power
SI: Diopter (D = m⁻¹)(1/f) = (1/v) - (1/u) | m = +v / u | Snell Law: n21 = sin(i) / sin(r) | Power (P) = 1 / f(in meters)
Power of combination of thin lenses: P_total = P1 + P2 + P3.
Variables: P is in Diopters (D). Convex lens: f > 0, P > 0; Concave lens: f < 0, P < 0
Exam Tip: Always convert focal length to METERS before computing P = 1/f in Diopters.
Chapter 2
Electricity & Circuits
Ohm Law & Resistance of Conductor
SI: Resistivity ρ in Ohm-meter (Ω·m)V = I × R | R = ρ × (L / A)
Ohm law states current through a conductor is directly proportional to voltage at constant temperature.
Variables: V = Potential Difference (Volt), I = Current (Ampere), R = Resistance (Ohm Ω), ρ = Resistivity (Ω·m), L = Length (m), A = Cross-sectional area (m²)
Exam Tip: If a wire is stretched to double its length (L -> 2L), its area halves (A -> A/2), so resistance becomes 4 times (R -> 4R)!
Series & Parallel Combinations & Electric Power
SI: Watt (W) for Power, Joule (J) for EnergySeries: R_s = R1 + R2 + R3 | Parallel: 1/R_p = 1/R1 + 1/R2 | Heat H = I²Rt | Power P = VI = I²R = V²/R
In series, current I is same; in parallel, voltage V is same across all resistors.
Variables: Electric Energy (Commercial unit) = 1 kWh = 1 Unit = 3.6 × 10⁶ Joules (J)
Exam Tip: Household circuits are always connected in parallel so each appliance gets full 220V and operates independently.