Year 9 Science Exam Review: Physics and Space Sciences

Comprehensive vocabulary flashcards covering Term 3 (circuits, waves, sound, anatomy of the ear and eye, optics, and heat transfer) and Term 4 (solar system structures, planetary motion, stellar life cycles, and cosmological theories) for Year 9 Science.

What is a closed circuit

An electrical circuit that forms an uninterrupted path, allowing the continuous flow of electrons ($\text{e}^-$) to occur.

Combination circuit

An electrical circuit (also known as a series-parallel circuit) that mixes series and parallel connections together in a single layout.

Current

The measure of the rate of flow of electric charge passing a point in a circuit, measured in amperes ($\text{A}$) using an ammeter connected in series.

Voltage

The measure of the amount of energy available to push charges around a circuit (or the energy required to move an electrical charge), measured in volts ($\text{V}$) using a voltmeter connected in parallel.

Resistance

The opposition to the flow of electrons within a material, resulting in the conversion of some electrical energy into heat energy, calculated as $R = \frac{V}{I}$ and measured in ohms ($\Omega$).

Ohm's Law

The principle stating that the electric current in a metallic conductor is directly proportional to the voltage drop across the conductor.

Transverse waves

Waves in which particles move up and down perpendicularly to the direction of wave travel, creating alternating high points (peaks) and low points (troughs).

Longitudinal waves

Waves in which particles move side to side parallel to the direction of wave travel, creating alternating regions of high pressure (compressions) and low pressure (rarefactions).

Compression

A high-pressure region in a longitudinal wave where the particles bunch closely together.

Rarefaction

A low-pressure region in a longitudinal wave where the particles are spread farthest apart.

Mechanical waves

Waves that require a physical material medium (such as a solid, liquid, or gas) to travel through (e.g., sound, water, and seismic waves).

Electromagnetic waves

Waves that do not require a medium and can travel through empty space or a vacuum at the speed of light ($3 \times 10^8\,\text{m/s}$).

Frequency

The number of complete waves that pass a fixed point in $1\,\text{second}$, measured in Hertz ($\text{Hz}$) and calculated as $f = \frac{1}{t}$.

Wavelength ($\lambda$)

The distance between two consecutive identical points on a wave, such as between two peaks or between two consecutive compressions.

Wave Equation

The mathematical formula relating wave speed, frequency, and wavelength: $v = f\lambda$, where $v$ is velocity in $\text{m/s}$, $f$ is frequency in $\text{Hz}$, and $\lambda$ is wavelength in $\text{m}$.

Pinna

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

Eardrum

A membrane that vibrates in response to incoming sound waves, transmitting these vibrations mechanically to the middle ear bones.

Cochlea

A spiral inner ear structure that converts incoming mechanical sound vibrations into electrical nerve impulses sent to the brain.

Eustachian tube

A passage in the ear that functions to equalise air pressure on both sides of the eardrum.

Auditory nerve

The sensory nerve bundle that carries electrical sound signals from the cochlea directly to the brain.

Law of Reflection

The optical principle stating that the angle of incidence is always equal to the angle of reflection.

Refraction

The bending of a wave when it speeds up or slows down as a result of crossing the boundary between mediums of different densities.

Dispersion

The splitting of white light into its component spectrum colours when passing through a prism due to different wavelengths refracting by different amounts.

Convex lens

A converging lens that causes parallel light rays passing through it to bend inward and meet at a focal point.

Concave lens

A diverging lens that causes parallel light rays passing through it to refract outward and spread apart.

Myopia

Short-sightedness, a condition where the focal image forms in front of the retina; corrected using a concave lens.

Hyperopia

Long-sightedness, a condition where the focal image forms behind the retina; corrected using a convex lens.

Cornea

A clear window located under the conjunctiva within the sclerotic layer that admits light into the eye.

Iris

The coloured structure located in front of the lens that changes size to regulate the amount of light entering the pupil.

Heat

The thermal energy transferred between particles, naturally flowing from a region of higher temperature to one of lower temperature.

Temperature

The measurement of the average kinetic energy of the particles making up a substance.

Conduction

The transfer of heat via direct physical contact between colliding particles, occurring most efficiently in solids.

Convection

The transfer of heat through fluids (liquids and gases) via the upward movement of warmer, less dense fluid and the sinking of cooler, denser fluid.

Thermal Radiation

The transfer of thermal energy via electromagnetic waves, capable of traveling freely through empty space or a vacuum.

Heliocentric model

The astronomical model in which the Sun rests near the center of the solar system while the Earth and other planets orbit around it.

Geocentric model

The historical astronomical model where Earth sits motionless at the center while the Sun, moon, planets, and stars revolve around it.

Terrestrial planets

Rocky planets primarily composed of rock and metal with solid, hard surfaces, comprising Mercury, Venus, Earth, and Mars.

Gas giants

Massive planets composed mostly of hydrogen and helium gases with deep swirling atmospheres and no solid surfaces (Jupiter and Saturn).

Ice giants

Large planets with small rocky cores surrounded mostly by heavier elements and an icy mixture of water, methane, and ammonia (Uranus and Neptune).

Light year

An astronomical unit of distance equal to the total distance light travels through a vacuum in $1\,\text{Earth year}$.

Astronomical Unit ($\text{AU}$)

A standard unit of measurement equal to the average distance between the Earth and the Sun ($1\,\text{AU}$).

Protostar

An early stage in stellar development where a collapsing gas cloud gathers mass from its parent cloud prior to initiating nuclear fusion.

Abiogenesis

The theory proposing that living organisms first originated on Earth from non-living, inorganic chemical substances in primordial seas.

Panspermia

The hypothesis proposing that life on Earth originated from microorganisms or simple cells that arrived from outer space aboard asteroids or meteors.

Kepler's Second Law

The orbital law stating that a planet's speed changes throughout its orbit, moving slowest when it is farthest from the central star.

Kepler's Third Law

The mathematical law stating that the ratio of orbital period squared to orbital distance cubed is constant for bodies orbiting the same mass: $\frac{T_1^2}{r_1^3} = \frac{T_2^2}{r_2^3}$.

Apparent magnitude

The measure of a star's brightness as observed from Earth, ranked on a scale from $-30$ (brightest) to $+30$ (dimmest).

Absolute magnitude

The actual, intrinsic brightness of a celestial object, independent of its distance from an observer.

Hertzsprung-Russell diagram

A scatter plot of stars showing the relationship between absolute magnitude (brightness on the y-axis) and surface temperature (decreasing toward the right on the x-axis).

Planck Curve

A graph showing the intensity of light and energy emitted at different wavelengths by an object based strictly on its temperature; as temperature increases, the peak shifts left and grows taller.

Steady State Theory

A rejected cosmological theory proposing that the universe has no beginning and continuously creates new matter to form stars and galaxies as space expands.

Big Bang Theory

The cosmological model stating that the universe originated approximately $14\text{ billion years}$ ago from a rapid cosmic explosion that brought time and space into existence.

Doppler effect

The apparent change in the observed frequency or pitch of a wave caused by the relative motion between the wave source and the observer.

Red shift

The lengthening of electromagnetic wavelengths emitted by celestial objects moving away from an observer, providing key evidence that the universe is expanding.

Hubble's Law

The astronomical law formulated by Edwin Hubble stating that galaxies are moving away from Earth at velocities directly proportional to their distance.

Cosmic Microwave Background Radiation

Uniform background radio noise detected across all regions of space, representing residual cooling radiation from the Big Bang corresponding to an average temperature of $-270^\circ\text{C}$.