Year 9 Physics Revision: Energy, Waves, Light, and Heat

Vocabulary review flashcards covering key definitions and principles of energy, wave mechanics, sound, light, heat transfer, and electricity from the Year 9 Physics study unit.

Wave

A disturbance that transfers energy from one place to another without transferring matter overall.

Transverse Wave

A wave in which the particles vibrate at right angles (perpendicular) to the direction the wave travels, such as light waves or water surface waves.

Longitudinal Wave

A wave in which the particles vibrate in the same direction (parallel) as the wave travels, such as sound waves or compression waves in a slinky.

Crest

The highest point of a transverse wave.

Trough

The lowest point of a transverse wave.

Amplitude

The maximum displacement or distance of a wave from its resting position (equilibrium). In sound, a higher amplitude corresponds to a louder sound.

Wavelength ($\lambda$)

The distance between two matching points on consecutive waves, such as from crest to crest or trough to trough, measured in metres.

Equilibrium

The central resting position of a wave where there is no disturbance.

Frequency ($f$)

The number of complete waves or vibrations that occur every second, measured in Hertz ($\text{Hz}$).

Pitch

A description of how high or low a sound seems, which is directly controlled by the wave's frequency (higher frequency results in higher pitch).

Medium

A physical substance or material (solid, liquid, or gas) through which a wave or energy travels.

Echo

A sound caused by the reflection of sound waves bouncing off a surface and returning to the ears after a noticeable delay.

Pinna

The external part of the ear that collects sound waves and directs them into the ear canal.

Ossicles

The three tiny bones in the middle ear (hammer, anvil, and stirrup) that amplify sound vibrations passed from the eardrum.

Cochlea

A fluid-filled structure in the inner ear containing tiny hair cells that convert mechanical vibrations into electrical nerve signals.

Auditory Nerve

The sensory pathway that carries electrical signals from the cochlea to the brain, where they are interpreted as sound.

Photon

A discrete particle or packet of electromagnetic energy used to describe light in the wave-particle model.

Visible Light Spectrum

The narrow band of electromagnetic radiation visible to humans, arranged from longest wavelength (lowest frequency) to shortest wavelength (highest frequency): Red, Orange, Yellow, Green, Blue, Indigo, Violet (ROYGBIV).

Dispersion

The separation of white light into its component colors when passing through a medium such as a prism or water droplets.

Reflection

The bouncing back of a wave (such as light or sound) when it hits an interface or surface.

Refraction

The change in direction (bending) of a wave as it travels from one medium into another because its speed changes.

Kinetic Energy ($\text{KE}$)

The form of energy an object possesses because of its motion.

Gravitational Potential Energy

The energy stored in an object because of its height above a reference point within a gravitational field.

Elastic Potential Energy

The energy stored when an elastic object is deformed by being stretched or compressed (such as a spring or rubber band).

Chemical Potential Energy

The energy stored in the chemical bonds of substances (such as food, petrol, coal, or batteries) that can be released or absorbed during reactions.

Law of Conservation of Energy

A fundamental scientific law stating that energy cannot be created or destroyed; it can only be transferred or transformed from one form to another.

Energy Transfer

The movement of energy from one object, place, or system to another without changing its form.

Energy Transformation

The process by which energy changes from one type or form into a different form (such as chemical energy to electrical energy).

Energy Efficiency

The percentage of total input energy that is converted into useful output energy, calculated using $\text{Efficiency} = \frac{\text{Useful energy output}}{\text{Total energy input}} \times 100\%$.

Sankey Diagram

A visual flow diagram that depicts energy transfers and transformations in a system, where arrow widths are drawn proportionally to the amounts of energy involved.

Heat

Thermal energy being transferred from an object or region of higher temperature to one of lower temperature due to a temperature difference.

Conduction

The transfer of thermal energy through direct physical contact between particles, primarily occurring in solids where vibrating particles pass energy to adjacent particles.

Convection

The transfer of thermal energy through the bulk movement of fluids (liquids and gases), occurring when heated, less dense fluid rises and cooler, denser fluid sinks.

Radiation

The transfer of thermal energy through electromagnetic waves, which requires no particles and can travel across a vacuum (empty space).

Convection Current

A circular flow pattern set up in a fluid as heated portions expand, decrease in density, and rise, while cooler, denser portions sink to replace them.

Thermal Conductor

A material (such as copper, aluminium, or iron) that readily permits the transfer of heat through particle interactions.

Thermal Insulator

A material (such as wood, plastic, rubber, or air) that slows down and impedes the transfer of thermal energy.

Electromagnetic Spectrum

The complete continuum of electromagnetic waves ordered from longest wavelength to shortest: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

Electric Current ($I$)

The rate of flow of electric charge through a conductor or circuit, measured in amperes ($\text{A}$).

Voltage ($V$)

The electrical potential difference between two points in a circuit that drives the flow of charge, measured in volts ($\text{V}$).

Electrical Resistance ($R$)

A measure of how strongly a material or component opposes the flow of electric current through it, measured in ohms ($\Omega$).