Unit 2: Waves and Electricity - Revision Notes

Comprehensive notes for IAL AS Physics Unit 2, covering theoretical concepts and mathematical applications.

1. Waves and Particle Nature of Light

1.1 Wave Properties

Waves transfer energy without the net transfer of matter. Progressive waves move through a medium, while stationary waves store energy.

• Amplitude: Maximum displacement from equilibrium.
• Frequency (f): Oscillations per second.
• Phase Difference: The fraction of a cycle between two points, measured in degrees or radians.

$$v=f\lambda$$

1.2 Refraction and Polarization

Refractive Index: A measure of how much light slows down in a material.

$$n=\frac{c}{v}$$

Snell's Law: Defines the path of light through two media.

$$n_1\sin {\theta }_1=n_2\sin {\theta }_2$$

1.3 Standing Waves and Interference

Formed by the superposition of two waves of the same frequency and amplitude traveling in opposite directions.

$$v=\sqrt{\frac{T}{\mu }}$$

1.4 Quantum Nature: Photoelectric Effect

Light consists of discrete packets of energy called photons. The photoelectric effect demonstrates the particle nature of electromagnetic radiation.

$$hf=\phi +\frac{1}{2}m{v}_{\max }^2$$

2. Electric Circuits

2.1 Basic Definitions

Current is the rate of flow of charge. Potential difference is the work done per unit charge.

$$I=\frac{\Delta Q}{\Delta t}\text{ and }V=\frac{W}{Q}$$

2.2 Drift Velocity

Current in a conductor is related to the number density of charge carriers ($n$), the charge ($q$), the cross-sectional area ($A$), and the drift velocity ($v$).

$$I=nqvA$$

2.3 Resistivity and Resistance

Resistance depends on the material's geometry and resistivity ($\rho$).

$$R=\frac{\rho l}{A}$$

2.4 Potential Dividers

A simple circuit that uses two or more resistors in series to supply a specific fraction of the input voltage.

$$V_{\text{out}}=\frac{R_2}{R_1+R_2}\times V_{\text{in}}$$

2.5 EMF and Internal Resistance

The Electromotive Force (e.m.f.) is the total energy supplied to each coulomb of charge by the source. Terminal p.d. is lower than e.m.f. due to internal resistance ($r$).

$$\epsilon =I(R+r)$$