Senior School Physics Comprehensive Physics Study Notes

Senior School Physics Curriculum and Essence

Physics is the study of natural phenomena through theories, laws, and experimental investigation. It is a key STEM subject aligned with Vision 2030 and Sessional Papers No. 1 of 2005 and No. 1 of 2019. The curriculum is anchored on Kolb Theory of Experiential Learning and Constructivism.

• Lesson Distribution: Compulsory areas receive $4$ lessons, while optional areas receive $6$. Each lesson is $40$ minutes.
• General Outcomes: Develop science process skills, critical thinking, innovation, and preparation for careers in STEM fields.

Mechanics and Thermal Physics

Introduction to Physics

• Branches: Mechanics, Electricity & Magnetism, Thermodynamics, Geometrical Optics, Waves, Electronics, Modern Physics, and Astronomy.
• Relationships: Intertwined with Mathematics (the language of physics), Chemistry (atomic interactions), Biology (biophysics), and Engineering (applied physics).

Pressure

• Atmospheric Pressure: Force per unit area exerted by air. Decreases with altitude. Demonstrated by the Crushing Can Experiment.
• Liquid Pressure ($P$): Calculated as $P = \rho gh$, where $\rho$ is density, $g$ is acceleration due to gravity ($9.8\,m/s^2$), and $h$ is depth.
• Pascal’s Principle: Pressure applied to an enclosed fluid is transmitted undiminished. Used in hydraulic jacks and brakes.

Mechanical Properties of Materials

• Key Properties: Ductility, Malleability, Elasticity, Brittleness, Strength, Hardness, and Stiffness.
• Hooke’s Law: $F = ke$, where $k$ is the spring constant and $e$ is extension.
• Stress and Strain:
  • Stress ($\sigma$): $\sigma = \frac{F}{A}$
  • Strain ($\epsilon$): $\epsilon = \frac{\Delta L}{L_0}$
  • Young’s Modulus ($Y$): $Y = \frac{\sigma}{\epsilon}$

Temperature and Thermal Expansion

• Units: Celsius (°C), Fahrenheit (°F), and Kelvin (K) (the SI unit).
  • $K = \text{°C} + 273.15$
• Linear Expansivity: $\Delta L = \alpha L_0 \Delta T$
• Anomalous Expansion: Water expands when cooled below $4\text{°C}$.

Moments and Equilibrium

• Center of Gravity (C.O.G): The point where an object's weight acts. Stability depends on its height and base width (Stable, Unstable, Neutral).
• Principle of Moments: For rotational equilibrium, $\sum \text{Clockwise Moments} = \sum \text{Counterclockwise Moments}$.
• Moment: $\text{Force} \times \text{Perpendicular distance}$.

Questions & Discussion

Q: Determine the weight of a 1m bar balanced at 30cm if a 0.6N force is at 70cm.
A: Using $0.6 \times 70 = W \times 30$, $W = 1.4\,N$.

Q: Why is it difficult to open a door from a point close to the hinges?
A: The perpendicular distance is small, resulting in insufficient moment; more force is required.

Q: State the Principle of Moments.
A: For a system in equilibrium, the sum of clockwise moments about a point must equal the sum of anticlockwise moments about the same point.

Energy, Work, Power, and Machines

• Kinetic Energy (KE): $KE = \frac{1}{2}mv^2$
• Gravitational Potential Energy (GPE): $GPE = mgh$
• Work and Power: $W = Fd$ and $P = \frac{W}{t}$.
• Machines: Include levers, inclined planes, pulleys, and gears.
  • Efficiency: Ratio of useful work output to total work input.

Waves and Optics

Properties of Waves

• Behaviors: Rectilinear propagation, Reflection, Refraction, Dispersion, Diffraction, and Interference.
• Stationary Waves: Formed by interference of two waves of equal frequency/amplitude moving in opposite directions. Feature Nodes and Antinodes.
• Doppler Effect: Change in frequency due to relative motion. Used in Radar, Ultrasound, and Astronomy (redshift).

Radioactivity and Isotopes

• Radiations: Alpha ($\alpha$), Beta ($\beta$), and Gamma ($\gamma$).
• Half-life ($t_{1/2}$): Time for half the sample to decay. $N(t) = N_0(\frac{1}{2})^{t/t_{1/2}}$.
• Nuclear Reactions: Fission (splitting) and Fusion (combining).

Electricity and Magnetism

Electrostatics

• Charging: Rubbing, Contact, Induction, and Separation. Like charges repel; unlike attract.
• Applications: Spray Guns, Photocopiers, Electrostatic Precipitators, and Lightning Arrestors.

Current Electricity

• Ohm’s Law: $V = IR$.
• Resistance ($R$): $R = \frac{\rho L}{A}$, where $\rho$ is resistivity.
• Power: $P = VI = I^2R = \frac{V^2}{R}$.
• Circuits:
  • Series: $R_{\text{total}} = R_1 + R_2 + ...$
  • Parallel: $\frac{1}{R_{\text{total}}} = \frac{1}{R_1} + \frac{1}{R_2} + ...$

Electronics

• Energy Bands: Valence band and Conduction band separated by a Band Gap.
• Materials: Insulators, Conductors, Semiconductors (Properties changed by Doping), and Superconductors.
• Semiconductors: N-type (pentavalent impurities) and P-type (trivalent impurities).

Environmental and Space Physics

Greenhouse Effect and Climate Change

• Gases: $CO_2$, $CH_4$, $N_2O$, and water vapor.
• Impacts: Ozone depletion, global warming, rising sea levels, and extreme weather.

Space Physics

• Big Bang Theory: The universe originated $13.8$ billion years ago.
• Kepler’s Laws: First (elliptical orbits), Second (equal areas), Third ($T^2 \propto r^3$).
• Celestial Bodies: Stars, Planets, Moons, Asteroids, Comets, Galaxies, and Nebulae.