| name | physics |
| description | CBSE Grade 10 Physics — Light, Electricity, Magnetism. Covers chapters 9-12 of Science. Activate for physics concepts, ray diagrams, circuit problems, and board exam patterns. |
Physics — CBSE Grade 10 Science
Syllabus Coverage (2026–27)
| Unit | Chapters | Marks |
|---|
| III. Natural Phenomena | Ch 9: Light – Reflection and Refraction, Ch 10: The Human Eye and the Colourful World | 12 |
| IV. Effects of Current | Ch 11: Electricity, Ch 12: Magnetic Effects of Electric Current | 13 |
| Physics Total | 4 Chapters | ~25 |
Chapter 9: Light – Reflection and Refraction
Key Concepts
Reflection:
- Laws of reflection: (i) angle of incidence = angle of reflection, (ii) incident ray, reflected ray, normal — all in same plane
- Concave mirror: converging, real images (except when object between F and P)
- Convex mirror: diverging, always virtual/erect/diminished images
- Mirror formula and magnification
Refraction:
- Laws of refraction (Snell's Law): n₁ sin i = n₂ sin r
- Refractive index: n = speed in vacuum / speed in medium
- Convex lens: converging, real images (except when object between F and O)
- Concave lens: diverging, always virtual/erect/diminished images
- Lens formula and magnification
- Power of lens
Key Formulas
MIRROR FORMULA: 1/v + 1/u = 1/f
MAGNIFICATION (mirror): m = -v/u = h'/h
Sign Convention (New Cartesian):
- Object always on left → u is always negative
- Concave mirror: f is negative, Convex mirror: f is positive
LENS FORMULA: 1/v - 1/u = 1/f
MAGNIFICATION (lens): m = v/u = h'/h
- Convex lens: f is positive, Concave lens: f is negative
POWER: P = 1/f (f in metres) → unit: Dioptre (D)
REFRACTIVE INDEX: n = sin i / sin r = c/v
n₂₁ = n₂/n₁ = v₁/v₂
COMBINED POWER: P = P₁ + P₂ + P₃ + ...
Image Formation Tables
Concave Mirror:
| Object Position | Image Position | Nature | Size |
|---|
| At infinity | At F | Real, inverted | Highly diminished |
| Beyond C | Between F and C | Real, inverted | Diminished |
| At C | At C | Real, inverted | Same size |
| Between C and F | Beyond C | Real, inverted | Enlarged |
| At F | At infinity | Real, inverted | Highly enlarged |
| Between F and P | Behind mirror | Virtual, erect | Enlarged |
Convex Lens:
| Object Position | Image Position | Nature | Size |
|---|
| At infinity | At F₂ | Real, inverted | Highly diminished |
| Beyond 2F₁ | Between F₂ and 2F₂ | Real, inverted | Diminished |
| At 2F₁ | At 2F₂ | Real, inverted | Same size |
| Between F₁ and 2F₁ | Beyond 2F₂ | Real, inverted | Enlarged |
| At F₁ | At infinity | Real, inverted | Highly enlarged |
| Between F₁ and O | Same side | Virtual, erect | Enlarged |
Common Exam Traps
- Sign convention errors — most common: forgetting u is always negative
- Not drawing the principal axis, lens/mirror properly in ray diagrams
- Confusing mirror magnification formula (negative sign) with lens formula
- Power of lens: forgetting to convert f to metres before calculating
Diagram Requirements (MUST draw in board exam)
- Ray diagram for concave mirror (at least 2 positions)
- Ray diagram for convex lens (at least 2 positions)
- At least 2 rays must be drawn for locating image
- Label: Principal axis, F, C/2F, object, image
Chapter 10: The Human Eye and the Colourful World
Key Concepts
- Structure of human eye: cornea, iris, pupil, lens, retina, optic nerve
- Power of accommodation: ability to focus on near and far objects
- Defects of vision:
- Myopia (near-sightedness): corrected by concave lens
- Hypermetropia (far-sightedness): corrected by convex lens
- Presbyopia: corrected by bifocal lens
- Atmospheric refraction: twinkling of stars, advanced sunrise/delayed sunset
- Dispersion: splitting of white light into 7 colours (VIBGYOR)
- Scattering of light: Tyndall effect, blue sky, red sunset
Key Formulas
MYOPIA correction: f = -far point distance (concave lens)
HYPERMETROPIA correction: f = near point distance (convex lens)
VIBGYOR: Violet, Indigo, Blue, Green, Yellow, Orange, Red
- Violet has shortest wavelength, highest frequency, maximum deviation
- Red has longest wavelength, lowest frequency, minimum deviation
Common Exam Traps
- Confusing myopia and hypermetropia corrections
- Not explaining WHY stars twinkle (atmospheric refraction due to changing density)
- Forgetting to mention Tyndall effect as cause of scattering phenomena
Chapter 11: Electricity
Key Concepts
- Electric current: I = Q/t (rate of flow of charge)
- Potential difference: V = W/Q (work done per unit charge)
- Ohm's Law: V = IR
- Resistance: R = ρl/A
- Series and parallel combinations
- Heating effect of current: Joule's law
- Electric power and energy
Key Formulas
CURRENT: I = Q/t (Ampere = Coulomb/second)
POTENTIAL DIFFERENCE: V = W/Q (Volt = Joule/Coulomb)
OHM'S LAW: V = IR
RESISTANCE: R = V/I (Ohm, Ω)
RESISTIVITY: R = ρl/A (ρ in Ω·m)
SERIES COMBINATION:
R_total = R₁ + R₂ + R₃ + ...
Same current through all resistors
V_total = V₁ + V₂ + V₃
PARALLEL COMBINATION:
1/R_total = 1/R₁ + 1/R₂ + 1/R₃ + ...
Same voltage across all resistors
I_total = I₁ + I₂ + I₃
JOULE'S LAW OF HEATING: H = I²Rt = VIt = V²t/R
ELECTRIC POWER: P = VI = I²R = V²/R (Watt)
ELECTRIC ENERGY: E = P × t = VIt (Joule)
1 kWh = 3.6 × 10⁶ J
Circuit Diagram Symbols
—/\/\/\— Resistor —|⊕|— Ammeter (series)
—||— Cell —⊗— Voltmeter (parallel)
—| |— Battery ○/ ○ Switch (open)
—→— Current direction ●—● Switch (closed)
Common Exam Traps
- Ammeter connected in SERIES, Voltmeter in PARALLEL — mixing these up
- Not drawing circuit diagrams neatly with proper symbols
- Confusing kWh and Joule conversions
- Forgetting that in parallel: total resistance < smallest individual resistance
- Not accounting for internal resistance when stated in problems
Chapter 12: Magnetic Effects of Electric Current
Key Concepts
- Magnetic field and field lines
- Right-hand thumb rule (for straight conductor)
- Solenoid: magnetic field like a bar magnet
- Force on current-carrying conductor in magnetic field (Fleming's Left Hand Rule)
- Electromagnetic induction (Faraday's law)
- Fleming's Right Hand Rule (for generators)
- Electric motor and Electric generator (AC and DC)
- Domestic electric circuits: fuse, earthing, short circuit
Key Rules
RIGHT-HAND THUMB RULE:
Thumb → direction of current
Fingers (curled) → direction of magnetic field
FLEMING'S LEFT HAND RULE (Motor):
Forefinger → magnetic Field
Middle finger → Current
Thumb → Force/Motion (thrust)
FLEMING'S RIGHT HAND RULE (Generator):
Thumb → Motion of conductor
Forefinger → magnetic Field
Middle finger → induced Current
Key Devices
ELECTRIC MOTOR: Converts electrical energy → mechanical energy
Uses: Fleming's Left Hand Rule
Parts: Coil, magnets, split ring commutator, brushes, axle
ELECTRIC GENERATOR: Converts mechanical energy → electrical energy
Uses: Electromagnetic induction (Fleming's Right Hand Rule)
AC Generator: slip rings → alternating current
DC Generator: split ring commutator → direct current
Domestic Circuits
Supply: 220V AC, 50Hz frequency
Fuse: thin wire with low melting point, connected in LIVE wire
Earthing: connected to metal body of appliances
Short circuit: live wire touches neutral wire → very high current → fuse melts
Overloading: too many appliances → current exceeds capacity → fuse melts
Three wires:
LIVE (red/brown) — high potential
NEUTRAL (black/blue) — zero potential
EARTH (green) — safety, connected to ground
Common Exam Traps
- Confusing Left Hand Rule (motor) with Right Hand Rule (generator)
- Not labeling all parts of motor/generator in diagrams
- Forgetting that AC generator uses slip rings, DC uses split rings
- Not mentioning the role of commutator (reverses current direction every half rotation)
High-Yield Topics (495+ Strategy)
- Electricity (Ohm's Law + Series/Parallel) — 5M LA question almost guaranteed
- Light (Mirror/Lens formula + Ray diagrams) — 5M LA in most papers
- Magnetic Effects (Motor/Generator) — 3-5M diagram-based question
- Human Eye defects — 2-3M frequently asked
- Case Study — Often from Electricity or Light chapter
CBSE Question Patterns
1-Mark MCQ Examples:
- "A concave mirror produces a real, inverted image of same size. The object is at: (a) F (b) C (c) Beyond C (d) Between F and C" → Answer: (b)
- "Which of the following has highest resistance? (a) 1Ω (b) 10⁵Ω (c) 10⁻⁵Ω (d) 10²Ω" → Answer: (b)
3-Mark SA Examples:
- "An object is placed at 30 cm from a concave mirror of focal length 15 cm. Find position, nature and size of image."
- "Three resistors of 5Ω, 10Ω and 15Ω are connected in parallel. Find equivalent resistance."
5-Mark LA Examples:
- "Draw ray diagrams for all 6 positions of object in a convex lens."
- "Derive the expression for equivalent resistance when three resistors are connected in (a) series (b) parallel."
Case Study Example:
- Passage about electricity bill of a household → calculate energy consumed, cost, suggest energy-saving measures
Answer Writing Framework for Physics
- Start with the formula — examiners check for this first
- Draw diagrams — ray diagrams, circuit diagrams earn dedicated marks
- Show all substitutions — V = IR, then V = 2 × 5 = 10V
- Include units in every answer — "R = 5 Ω", "P = 100 W"
- For derivations — start from basic principle, proceed step by step
- For diagram-based questions — label every component, use ruler for straight lines
Internal Assessment Notes
| Component | Details |
|---|
| Practical Exam | Perform experiments: focal length of concave mirror/convex lens, Ohm's law verification, resistances in series/parallel |
| Practical viva | Be prepared for "why" questions about the experiment |
| Record maintenance | All observations with proper tables, calculations, and results |
