OpenRevise GCSE

Physics · Paper 2

Waves

Transverse and longitudinal waves, properties of waves, reflection and refraction, sound and ultrasound, the electromagnetic spectrum, lenses, visible light and black body radiation.

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Key terms in this chapter

All 72, gathered from every lesson.

Transverse wave
A wave with vibrations at right angles to the direction of travel.
Longitudinal wave
A wave with vibrations parallel to the direction of travel.
Compression
A region where particles are close together.
Rarefaction
A region where particles are spread out.
Medium
The material a wave travels through.
Oscillation
A back-and-forth movement.
Ear drum
A thin membrane in the ear that vibrates with sound.
Cochlea
A coiled part of the inner ear that turns vibrations into signals.
Frequency range
The span of frequencies a device or ear can respond to.
Infrasound
Sound below 20 Hz.
Ultrasound
Sound above 20 kHz.
Vibration
A repeated back-and-forth movement.
Ultrasound
Sound with frequency above 20 kHz.
Echo
A reflection of a sound wave.
Seismic wave
A wave produced by an earthquake.
P-wave
A longitudinal seismic wave.
S-wave
A transverse seismic wave that cannot travel through liquids.
Echo sounding
Using reflected sound to find depth.
Electromagnetic wave
A transverse wave that can travel through a vacuum.
Spectrum
A continuous range of wavelengths or frequencies.
Radio wave
The electromagnetic wave with the longest wavelength.
Gamma ray
The electromagnetic wave with the shortest wavelength.
Visible light
The part of the spectrum our eyes detect.
Absorber
An object that takes in the energy of a wave.
Ionising radiation
Radiation that can remove electrons from atoms.
Radiation dose
A measure of the risk of harm from exposure to radiation.
Sievert
The unit of radiation dose.
Millisievert
One thousandth of a sievert.
Mutation
A change in the genes of a cell.
Aerial
A device that transmits or receives radio waves.
Satellite communication
Sending signals to and from satellites, using microwaves.
Fibre optics
Glass fibres that carry light signals.
Medical imaging
Making pictures of the inside of the body.
Radiotherapy
Using radiation to treat cancer.
Thermal camera
A camera that detects infrared.
Sterilise
Kill bacteria, e.g. using gamma rays.
Convex lens
A lens that brings parallel rays to a focus.
Concave lens
A lens that spreads parallel rays out.
Principal focus
The point where parallel rays meet after a convex lens.
Focal length
The distance from the lens to the principal focus.
Real image
An image formed where light rays actually meet.
Virtual image
An image formed where rays appear to come from.
Specular reflection
Reflection from a smooth surface in a single direction.
Diffuse reflection
Reflection from a rough surface in many directions.
Colour filter
Material that transmits some wavelengths and absorbs others.
Transparent
Lets light pass through with no scattering.
Translucent
Lets light through but scatters it.
Opaque
Does not let light through.
Amplitude
The maximum displacement of a point on a wave from its undisturbed position.
Wavelength
The distance from a point on one wave to the same point on the next wave.
Frequency
The number of waves passing a point each second.
Period
The time for one complete wave.
Wave speed
The speed at which energy is transferred through a medium.
Ripple tank
A shallow tray of water used to show wave behaviour.
Reflection
When a wave bounces off a surface.
Absorption
When a wave's energy is taken in by a material.
Transmission
When a wave passes through a material.
Normal
A line at right angles to a surface.
Angle of incidence
The angle between the incident ray and the normal.
Angle of reflection
The angle between the reflected ray and the normal.
Refraction
A change in direction of a wave caused by a change in speed.
Normal
A line at right angles to the boundary.
Angle of refraction
The angle between the refracted ray and the normal.
Wavefront
A line showing all points of a wave at the same stage.
Denser medium
A medium in which the wave travels more slowly.
Boundary
The surface between two media.
Black body
An object that absorbs all the radiation that hits it.
Emit
Give out radiation.
Absorb
Take in radiation.
Intensity
The amount of radiation per second per unit area.
Infrared
Electromagnetic radiation emitted by all objects.
Equilibrium
When absorption equals emission.