Year 9 Science: Waves, Sound and Light

Comprehensive vocabulary flashcards covering the physics of mechanical and electromagnetic waves, sound characteristics, and the properties of light.

Mechanical waves

Waves that require a medium (matter) to move energy, where the matter moves for a short period before returning to its starting position.

Transverse waves

Waves where the individual particles move perpendicular to the motion of the wave, such as water ripples or EM waves.

Longitudinal waves

Waves where the particles move parallel to the motion of the wave, such as sound waves.

Period

How long it takes for a wave to go through one wavelength, measured in seconds ($s$).

Frequency

How many wavelengths go by in a second, measured in Hertz ($Hz$).

Wavelength

The distance between one crest of a wave and the next crest, or trough to trough, measured in meters ($m$).

Amplitude

The maximum displacement of the particles in a mechanical wave from their rest point.

Wave equation

The relationship between speed ($v$), frequency ($f$), and wavelength ($\lambda$), expressed as $v = f \times \lambda$.

Speed of Light

The velocity of light in a vacuum, which is $3 \times 10^8\,\text{ms}^{-1}$.

Speed of Sound

The velocity at which sound travels, which is $343\,\text{ms}^{-1}$.

Compressions

The regions in a longitudinal sound wave that act as peaks to transfer energy.

Rarefaction

The regions in a longitudinal sound wave that act as troughs to transfer energy.

Pitch

How high or low a sound is, determined by the frequency of the sound wave.

Doppler effect

A phenomenon where the pitch of a sound changes as the source moves either toward or away from an observer.

Echo

The reflection of a sound wave off of a surface.

Sonar

An acronym for Sound Navigation and Ranging, used by ships and submarines to locate objects underwater.

Echolocation

A navigation and hunting technique used by animals like bats and whales that involves the reflection of sound.

Electromagnetic (EM) Waves

Transverse waves made of self-propagating magnetic and electric fields that can travel through empty space (a vacuum).

Visible light spectrum

The only part of the electromagnetic spectrum visible to the naked eye, organized by colors in the acronym ROY G BIV.

Bioluminescence

The process by which a living thing produces its own light through chemical reactions.

Reflection

A property of light where waves bounce off a surface.

Refraction

The bending of light as it moves from one medium into another because its speed changes.

Diffraction

When light waves spread out while passing through gaps or bend around obstacles.

Polarise

The process of filtering light to allow it to move only in particular directions.

Disperse

The separation of light into its individual colors due to differences in frequency.

Transmission

The property of light passing through an object without being absorbed.

Transparent

A clear object that allows light to pass through it.

Translucent

An object that allows light to pass through but blurs the image behind it.

Opaque

An object that does not transmit light.