# Module 4 – Electrons

## Wave-particle DualityWave-particle Duality

Wave-particle duality is a model used to describe how all matter has both wave and particle properties. For example, under certain conditions, electrons can be made to diffract. They spread out like waves as they pass through a tiny gap (thin slice of polycrystalline...

## The Photoelectric EffectThe Photoelectric Effect

The photoelectric effect is the process by which photons of electromagnetic radiation shone onto a metal cause photoelectric emission of electrons from its surface. This is demonstrated by the gold leaf electroscope.  The top plate is charged by briefly touching it...

## PhotonsPhotons

Electromagnetic radiation has particulate, as well as wave, nature. A photon is the quantum pf energy of this EM radiation (quantised describes something that takes discrete values).  Energy of a photon is given by the equation = ℎ and therefore  is Planck’s constant,...

## Stationary WavesStationary Waves

A stationary wave forms when two progressive waves with the same frequency travelling in opposite directions are superposed. As they have same frequency, at certain point the are interphase (node) and at other points they are in phase (antinode). The separation...

## SuperpositionSuperposition

The principle of superposition of waves states that when two waves meet at a point the resultant displacement at that point is equal to the vector sum of the displacements of the individual waves.  If two progressive waves are in phase then the maximum positive...

## Electromagnetic WavesElectromagnetic Waves

Electromagnetic waves are transverse waves comprising of electric and magnetic fields oscillating at right angles to each other.  Different types of EM waves are classified by wavelength. Type of EM wave Wavelength Radio waves  Microwaves Infrared Visible Ultraviolet...

## Wave MotionWave Motion

Progressive waves are oscillations that travel through matter (or vacuum), transferring energy from one place to another, but not matter. In a transverse wave the oscillations are perpendicular to the direction of energy transfer (e.g. electromagnetic waves, waves on...

## Circuit SymbolsCircuit Symbols

Consult the textbook or the internet.

## Potential DividersPotential Dividers

Potential dividers are electric circuits that divide the potential difference across two or more components (often two resistors) in order to produce a specific output. Potential dividers function by the fact that the p.d. across each resistor depends on its...

## Internal ResistanceInternal Resistance

When current flows through a power source, some energy is lost and not all energy transferred to the charge is available for the circuit. The terminal p.d. is the measured at the terminals of the power source is therefore less than the actual e.m.f., and this...

## Series and Parallel CircuitsSeries and Parallel Circuits

In series circuits, there is only one possible path for the current. The current is the same in every position and the sum of the e.m.f.s equals the sum of the IR products. In parallel circuits, there is more than one possible path for the current. How much charge...

## PowerPower

Power is the rate of energy transfer by each electrical component. This equation can be combined with = × to give two additional equations for power: Since = , this equation also yields:

## ResistivityResistivity

Resistivity is a property of a material, measured in Ωm, defined as the product of the resistance of a component made of the material and its cross sectional area divided by its length at a given temperature.  Good conductors have a very low resistivity (in the order...

## ResistanceResistance

The resistance of a component is defined as the ratio between V and I. Its unit is the ohm, where  Ohm’s law states that, for metallic conductor kept at a constant temperature, the current in a wire is directly proportional to the p.d. across its ends.  Resistance...

## Electromotive Force and Potential DifferenceElectromotive Force and Potential Difference

Potential difference is a measure of the transfer of energy by charge carriers; its unit is the volt where one volt is the p.d. across a component when 1J of energy is transferred per unit charge passing through the component. In this equation, V is the p.d. measured...

## Mean Drift VelocityMean Drift Velocity

Mean drift velocity is the average velocity of electrons as they move through a wire. Its symbol is v and its unit is ms-1. Charge carriers actually move slowly as free electrons repeatedly collide with the positive metal ions as they drift through the wire towards...

## ChargeCharge

Electric current is defined as the rate of flow of charge, and it is measured in amperes. It is the amount of current passing a point in the circuit per unit time.  Electric charge is measured in coulombs, where one coulomb is the electric charge flowing past a point...

## STATIONARY WAVES: Part 3STATIONARY WAVES: Part 3

1. Stationary Wave: A stationary/standing wave is the superposition of two progressive waves with the same wavelength, moving in opposite directions. 2. As the waves, of the same wavelength and frequency meet at a point, the points where they interfere destructively...