📌 Welcome to Your Third Term Revision!
This comprehensive revision covers all the topics from the Third Term. Use this to:
- Review key concepts from each topic
- Practice with revision questions
- Prepare for your end-of-term examination
- Identify areas that need more attention
Topics Covered in Third Term
| Week |
Topic |
Key Concepts |
| 2 |
Magnetism |
Magnetic fields, domain theory, Earth's magnetism, angle of dip/declination |
| 3 |
Electromagnetic Induction |
Faraday's Law, Lenz's Law, generators, motors, transformers |
| 4 |
Wave-Particle Duality |
Photoelectric effect, Einstein's equation, de Broglie wavelength |
| 5 |
Nuclear Physics |
Atomic structure, radioactivity, α/β/γ radiation, half-life, fission/fusion |
| 6 |
Energy Production |
Renewable/non-renewable energy, solar, wind, hydro, nuclear, efficiency |
| 7 |
Satellite Communication |
Orbits (GEO, MEO, LEO), GPS, frequency bands, uplink/downlink |
| 8 |
Optical Instruments |
Microscope, telescope, periscope, camera, magnification |
Topic 1: Magnetism – Summary
🔑 Key Points:
- Magnetic Field: Region around a magnet where force is felt. Lines go from N → S outside, S → N inside.
- Domain Theory: Magnetic materials consist of tiny domains. Aligned = magnetised; random = unmagnetised.
- Earth's Magnetism: Earth is a giant magnet. Geographic North = Magnetic South. Angle of dip = 0° at equator, 90° at poles.
- Materials: Ferromagnetic (Fe, Co, Ni) – strongly attracted; Paramagnetic (Al) – weakly attracted; Diamagnetic (Cu) – weakly repelled.
Topic 2: Electromagnetic Induction – Summary
🔑 Key Points:
- Faraday's Law: ε = −N × (ΔΦ/Δt). Induced EMF is proportional to rate of change of flux.
- Lenz's Law: Induced current opposes the change that produced it. Explains the negative sign.
- Generators: Mechanical → Electrical (AC or DC).
- Motors: Electrical → Mechanical (back EMF).
- Transformers: Vs/Vp = Ns/Np = Ip/Is
Topic 3: Wave-Particle Duality – Summary
🔑 Key Points:
- Photoelectric Effect: Ek = hf − φ. Electrons emitted when light frequency exceeds threshold.
- Photon Energy: E = hf = hc/λ
- de Broglie Wavelength: λ = h/(mv). Matter has wave properties.
- Wave Properties: Interference, diffraction, polarization.
- Particle Properties: Photoelectric effect, Compton scattering.
Topic 4: Nuclear Physics – Summary
🔑 Key Points:
- Atomic Structure: Nucleus (protons + neutrons) + electrons. Atomic notation: AZX
- Radioactivity: α (He nucleus, low penetration), β (electron, medium), γ (EM wave, high penetration).
- Half-Life: N = N₀ × (½)t/T. Time for half of atoms to decay.
- Fission: Splits heavy nuclei → energy (nuclear reactors).
- Fusion: Combines light nuclei → energy (stars, cleaner).
Topic 5: Energy Production – Summary
🔑 Key Points:
- Non-Renewable: Coal, oil, natural gas, nuclear (finite, high emissions).
- Renewable: Solar, wind, hydro, geothermal, biomass (inexhaustible, low emissions).
- Efficiency: η = (Useful Output / Input) × 100%
- Solar: P = A × I × η
- Wind: P = ½ρAv³Cp
- Hydro: P = ρgQhη
Topic 6: Satellite Communication – Summary
🔑 Key Points:
- Orbits: GEO (35,786 km, stationary), MEO (GPS), LEO (ISS, Starlink).
- Orbital Velocity: v = √(GM/r)
- GPS: 24+ satellites, triangulation, needs ≥4 satellites.
- Uplink: Earth → Satellite; Downlink: Satellite → Earth.
- Frequency Bands: L (1-2 GHz), S, C, X, Ku (12-18 GHz), Ka (26-40 GHz).
Topic 7: Optical Instruments – Summary
🔑 Key Points:
- Microscope: Uses objective + eyepiece (both convex). Total M = Mobj × Meye.
- Telescope: Uses objective (lens/mirror) + eyepiece. M = fobj / feye.
- Periscope: Uses two mirrors at 45°. No magnification, changes line of sight.
- Camera: Lens focuses light on sensor. Aperture controls light; shutter controls exposure.
- Magnification: m = hᵢ/hₒ = v/u
Key Formulas Summary
| Topic |
Formula |
Variables |
| Electromagnetic Induction |
ε = −N(ΔΦ/Δt) |
ε = EMF, N = turns, Φ = flux |
| Transformer |
Vs/Vp = Ns/Np |
V = voltage, N = turns |
| Photoelectric Effect |
Ek = hf − φ |
Ek = kinetic energy, φ = work function |
| de Broglie Wavelength |
λ = h/(mv) |
λ = wavelength, m = mass, v = velocity |
| Half-Life |
N = N₀(½)t/T |
N = remaining, T = half-life |
| Orbital Velocity |
v = √(GM/r) |
G = gravitational constant, M = Earth's mass |
| Magnification |
m = hᵢ/hₒ = v/u |
h = height, v = image distance, u = object distance |
Revision Questions
Test your understanding of all Third Term topics:
Section A: Multiple Choice (Choose the correct option)
- The region around a magnet where magnetic force can be felt is called:
A) Magnetic pole B) Magnetic field C) Magnetic domain D) Magnetic flux
- According to Faraday's Law, the induced EMF is proportional to:
A) The magnetic field strength B) The rate of change of flux C) The area of the coil D) The current
- The photoelectric effect proves that light has:
A) Wave properties only B) Particle properties only C) Both wave and particle properties D) Neither wave nor particle properties
- Which type of radiation has the highest penetrating power?
A) Alpha B) Beta C) Gamma D) X-rays
- A satellite in geostationary orbit is at approximately:
A) 1,000 km B) 10,000 km C) 35,786 km D) 200,000 km
- The total magnification of a compound microscope is the product of:
A) Objective × Eyepiece B) Objective + Eyepiece C) Objective / Eyepiece D) Objective − Eyepiece
- Which of the following is a renewable energy source?
A) Coal B) Oil C) Natural Gas D) Solar
- The half-life of a radioactive substance is the time for:
A) All atoms to decay B) Half of the atoms to decay C) The activity to double D) The mass to double
Answers: 1-B, 2-B, 3-C, 4-C, 5-C, 6-A, 7-D, 8-B
Section B: Short Answer Questions
- State Lenz's Law and explain its significance in electromagnetic induction.
- Write Einstein's photoelectric equation and define each term.
- Distinguish between nuclear fission and nuclear fusion.
- What is the difference between a geostationary satellite and a low Earth orbit satellite?
- Draw a labelled diagram of a compound microscope.
Section C: Calculation Questions
- A coil has 300 turns. The magnetic flux changes from 0.06 Wb to 0.01 Wb in 0.02 seconds. Calculate the induced EMF.
- A metal has a work function of 2.5 eV. Calculate the threshold frequency for this metal. (h = 6.63 × 10⁻³⁴ J·s, 1 eV = 1.6 × 10⁻¹⁹ J)
- A radioactive sample has a half-life of 6 days. If the initial mass is 48 g, what mass remains after 18 days?
- A telescope has an objective lens with focal length 120 cm and an eyepiece with focal length 4 cm. Calculate its magnification.
- Calculate the orbital velocity of a satellite at an altitude of 500 km above the Earth's surface. (R_E = 6.37 × 10⁶ m, M = 5.97 × 10²⁴ kg, G = 6.67 × 10⁻¹¹ N·m²/kg²)
Answers to Section B
1. Lenz's Law: The induced current flows in a direction that opposes the change that produced it. It ensures energy conservation and gives the negative sign in Faraday's Law.
2. Ek = hf − φ. Ek = maximum kinetic energy, hf = photon energy, φ = work function.
3. Fission splits heavy nuclei into lighter ones; fusion combines light nuclei into heavier ones. Fission is used in nuclear reactors; fusion powers the sun.
4. Geostationary (GEO) is at 35,786 km and appears stationary; LEO is below 2,000 km and moves fast around the Earth.
5. (Diagram: objective lens at bottom, eyepiece at top, light path through the tube).
Answers to Section C
1. ε = −N(ΔΦ/Δt) = −300 × ((0.01−0.06)/0.02) = −300 × (−2.5) = 750 V
2. f₀ = φ/h = (2.5 × 1.6 × 10⁻¹⁹) / (6.63 × 10⁻³⁴) = 6.03 × 10¹⁴ Hz
3. n = 18/6 = 3 half-lives. N = 48 × (½)³ = 48 × ⅛ = 6 g
4. M = fobj / feye = 120/4 = 30×
5. r = 6.37×10⁶ + 0.5×10⁶ = 6.87×10⁶ m; v = √(GM/r) = √((6.67×10⁻¹¹ × 5.97×10²⁴) / (6.87×10⁶)) = √(5.80×10⁷) = 7.62 km/s
Examination Preparation Tips
📌 Tips for Success:
- Review all formulas – make a formula sheet and memorise them.
- Understand key definitions – be able to explain concepts in your own words.
- Practice calculations – work through all examples and assignment questions.
- Draw diagrams – practice drawing field lines, ray diagrams, and circuit diagrams.
- Know your units – be familiar with SI units for all quantities.
- Time management – allocate time for each section during the exam.
- Read questions carefully – identify what is being asked before answering.