GCSE Physics Units 1.3, 1.5, and 1.6: Waves, Heat Transfer, and Density

Vocabulary practice flashcards covering wave features, heat transfer mechanisms, density calculations, and total internal reflection for GCSE Physics Unit 1.

Transverse wave

A wave in which vibrations are at $90^\circ$ to the direction of travel.

Longitudinal wave

A wave in which vibrations are parallel to the direction of travel.

Wavelength

The length of one complete wave.

Amplitude

The maximum displacement of a wave.

Frequency

The number of waves produced or passing a point in $1\,\text{second}$, measured in hertz ($\text{Hz}$).

Wave speed equations

$\text{Speed (m/s)} = \frac{\text{distance (m)}}{\text{time (s)}}$ and $\text{Wave speed} = \text{wavelength (m)} \times \text{frequency (Hz)}$.

Geosynchronous satellite

A satellite that takes $24\,\text{hours}$ to orbit Earth and returns to the same point once every $24\,\text{hours}$.

Geostationary satellite

A satellite that takes $24\,\text{hours}$ to orbit Earth and stays directly above the same point on Earth at all times.

Refraction

The change in direction and wavelength of a wave due to a change in speed when passing between media of different optical densities.

Law of reflection

The principle that the angle from the normal to the wave when it hits an object is equal to the angle when it is reflected, with no change in wavelength.

Electromagnetic spectrum

A continuous family of transverse waves that all transfer energy and travel at the same speed in a vacuum ($3 \times 10^8\,\text{m/s}$).

Conduction

The transfer of heat in solids where thermal energy causes particles to vibrate more and transfer energy to neighboring particles as they collide.

Free electrons

Delocalized particles found in metals that carry heat energy quickly from the hot side to the cold side, making metals the best thermal conductors.

Convection

The transfer of heat in liquids and gases occurring when heated fluid particles move quicker and spread further apart, becoming less dense and rising.

Convection current

A circulating flow created in a fluid when warmer, less dense fluid rises above cooler, denser fluid.

Thermal radiation

Heat transfer in the form of infrared waves emitted in all directions by all warm objects, capable of traveling through solids, liquids, gases, and a vacuum.

Black surfaces (thermal radiation)

Surfaces that absorb infrared radiation best and emit infrared radiation best.

Shiny surfaces (thermal radiation)

Surfaces that reflect infrared radiation well but are poor emitters and poor absorbers.

Payback time

The time required to save the same amount of money as the initial cost of installing insulation, calculated as $\text{Payback time} = \frac{\text{installation cost}}{\text{annual savings}}$.

Density

The mass per unit volume of a substance, calculated as $\text{density} = \frac{\text{mass}}{\text{volume}}$ and measured in $\text{g/cm}^3$ or $\text{kg/m}^3$.

Displacement method (for density)

A technique to determine the volume of an irregularly shaped solid by measuring the volume of water it displaces inside a measuring cylinder.

Critical angle

The angle of incidence at which light refracts along the boundary between two media of differing optical densities.

Total internal reflection

The complete reflection of a ray of light back into the medium when travelling from higher to lower optical density at an angle greater than the critical angle.

Optical fibre

A thin glass tube that transmits light or infrared waves over long distances via repeated total internal reflection along its walls.

Endoscope

A medical instrument using total internal reflection in optical fibres to illuminate and investigate specific areas inside the body in detail without ionizing radiation.

CT scan

A medical imaging procedure using $\text{X rays}$ to create detailed $3\text{D}$ images of the entire body, posing a higher risk due to ionizing radiation.