Y9 Physics

Wave motion

The transfer of energy without the transfer of matter

Wavelength

The distance between two successive waves usually measured in metres

Amplitude

The maximum distance a wave extends beyond its middle position

Frequency

The rate at which a repeating event occurs per unit of time

Crest

The highest point of a transversal wave

Trough

The lowest point of a transversal wave

Periodic motion

Movement that is repeated at regular intervals

Period

The time it takes for a wave to complete one cycle

Cycle

One complete repetition of a periodic motion or waveform

Electromagnetic spectrum

The complete range of electromagnetic radiation, from radio to gamma rays

Light

A form of electromagnetic radiation visible to the human eye

Ray

A straight arrow, showing the direction of light from the source to the surface

Beam

Parallel rays made visible by the scattering of light

Point source

An ideal source that emits light equally from all directions

Luminous object

An object that emits light

Non-luminous object

An object that does not produce its own light, and is made visible by the reflection of light from a luminous source

Incandescence

The production of light by burning

Bioluminescence

The production of light from a living organism

Transmission

When light goes through the surface of an object

Reflection

When light bounces back off the surface of an object

Opaque

When light does not pass through a material

Transparent

When all light passes through a material

Translucent

When some light passes through a material

Absorption

When light goes in the surface and is usually converted into heat energy

Diffuse reflection

When light reflects off a rough surface, and the light reflects in different directions and creates a distorted image

Regular reflection

When light reflects off a smooth surface, and reflects a clear image

Refraction

When light goes through a different medium and changes speed, causing the light to change direction

Refractive index

Relative measure of the bending of a ray of light when passing from one medium into another

Dispersion

When the different wavelengths of white light refract and move at different speeds, spreading into the full spectrum of visible light

Lens

An object made of a transparent material that refracts light

Concave lens

A type of lens that diverges light

Convex lens

A type of lens that converges light

Convergence

When rays of light bend inwards towards the focal point

Divergence

When rays of light bend outwards away from each other

Focal point

The point when converged rays meet

Focal length

The distance between the optical centre and the focal point

Optical centre

The geometric centre of the lens

Density

The amount of mass per unit volume of medium

Curvature

How curved a surface is

Profile

The shape of the lens