Physical Science Last Minute Revision
Quick-fire revision for BSE Telangana Class 10 Physical Science — must-know Physics formulas, Chemistry reactions, light recall, and exam tips for the final 24 hours.
Ch. 1 & 4 — Light Formulas
- →Mirror: 1/f = 1/v + 1/u · m = −v/u · f = R/2 (concave f−ve, convex f+ve)
- →Lens: 1/f = 1/v − 1/u · m = v/u · Power P = 1/f(metres)
- →Snell's Law: n₁sinθ₁ = n₂sinθ₂ · n = c/v = sinᵢ/sinr
- →Concave mirror → real, inverted image (for objects beyond F) · Convex mirror → always virtual, erect, small
- →Myopia: concave (−ve P) · Hypermetropia: convex (+ve P) · Presbyopia: bifocal
Ch. 2 & 3 — Reactions to Remember
- →CaCO₃ → CaO + CO₂ (heat) · 2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂ (heat) — decomposition
- →Zn + H₂SO₄ → ZnSO₄ + H₂ · HCl + NaOH → NaCl + H₂O — acid reactions
- →Fe + CuSO₄ → FeSO₄ + Cu (Fe displaces Cu — displacement) · BaCl₂ + Na₂SO₄ → BaSO₄↓ + 2NaCl
- →2NaHCO₃ → Na₂CO₃ + H₂O + CO₂ (heat) · Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O (bleaching powder)
- →pH < 7 = acidic · pH = 7 = neutral · pH > 7 = basic
Ch. 6 & 7 — Atom and Periodic Table
- →Max e⁻ per shell = 2n² (K:2, L:8, M:18) · Valency = outermost e⁻ (or 8 − outermost if >4)
- →Z = protons · A = protons + neutrons · Isotopes = same Z, different A
- →Period → left to right: atomic radius ↓, electronegativity ↑, metallic character ↓
- →Group → top to bottom: atomic radius ↑, metallic character ↑, electronegativity ↓
- →Groups 1 (alkali metals) and 17 (halogens): memorise properties and reactions
Ch. 9 — Electric Current
- →V = IR · P = VI = I²R = V²/R · H = I²Rt · 1 kWh = 3.6 × 10⁶ J
- →Series: R_total = R₁+R₂+R₃ (same current) · Parallel: 1/R = 1/R₁+1/R₂+1/R₃ (same voltage)
- →Ammeter: series, low resistance · Voltmeter: parallel, high resistance
- →Conventional current: + to − externally · Electron flow: − to + externally
Ch. 11 — Metallurgy Quick Points
- →Reactivity series: Na>Mg>Al>Zn>Fe>Pb>H>Cu>Ag>Au — more reactive = higher
- →Thermite: Fe₂O₃ + 2Al → Al₂O₃ + 2Fe — Al reduces Fe; used in rail welding
- →Electrolytic refining: impure metal = anode, pure metal = cathode
- →Alloys: Steel (Fe+C) · Brass (Cu+Zn) · Bronze (Cu+Sn) · Stainless steel (Fe+Cr+Ni)
Exam Day Strategy
- →Physical Science Paper: 50 marks (Part A — Physics, Part B — Chemistry, roughly equal)
- →Numericals: always write formula → substitute with units → calculate. Never skip formula.
- →Diagrams: label every part clearly — unlabelled diagrams lose marks
- →Chemical equations: balance all equations — unbalanced equation is incorrect
- →Activity chapters (Ch. 5, 8, 10, 12): these are project-based — focus on definitions and key reactions