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P5 – Key Words
Accelerate
Action (force)
Aerial
Amplifies
(in) Antiphase
Angle of incidence
Angle of refraction
Aperture
Camera
Cancellation
Centripetal force
Coherent
Concave
Condenser lens
Constructive
(interference)
Converging
Convex
Crests
Critical angle
Decelerate
Destructive
(interference)
An object accelerates if it speeds up
Applying a force on an object
A device for receiving or transmitting radio signals
Increases the size e.g. a radio signal
When two waves are “out of step” with each other; crests
coincide with troughs
The angle between the incident ray of light and the normal
at a given point
The angle between the refracted ray of light and the
normal at a given point.
The size of the hole through which light enters a camera
An optical instrument that produces a reduced image on a
piece of film (film camera) or light sensitive chip (digital
camera)
When two waves cancel to give reduced amplitude;
destructive interference
Force towards the centre of a circle essential for circular
motion
Waves having the same frequency, amplitude and phase (or
constant phase difference)
Curving inwards
Used in a projector to concentrate light on a slide
When two waves combine to give increased amplitude
Coming towards a point
Curving outwards
Peaks of a wave
The angle of incidence for which the angle of refraction is
90°; larger angles of incidence result in total internal
reflection (TIR)
An object decelerates if it slows down
When two waves cancel out to give reduced amplitude
Diffraction
Digital signal
Dispersion
Diverging
Electromagnetic waves
Focal length
Focal plane
Focal point
Focus
Frequency
Fringes
Geostationary satellite
Global Positioning
System (GPS)
Gravitational
attraction
Gravitational field
Gravity
Interference
Inverse square law
Inverted
Ionosphere
The spreading out of a wave when it passes through a gap
or around an edge. Maximum diffraction occurs when the
gap width is equal in size to the wavelength of the wave.
A signal which is either “on” or “off”
The splitting of light into its different wavelengths
Spreading out/moving away from a point
A group of waves that carry different amounts of energy –
range from low frequency radio waves to high frequency
gamma rays.
The distance from the optical centre of a lens to its focus
The plane that includes the focus (focal point)
Focus (of a lens)
(of a lens or mirror) the point to which rays of light
converge or from which they diverge
Number of vibrations per second, frequency is measured in
Hertz (Hz).
Light and dark bands of light produced by two-slit
interference of monochromatic (single wavelength) light
A satellite in orbit above the equator taking 24 hours for
one orbit
A satellite navigation system that involves many satellites
orbiting Earth
Force of attraction between two bodies due to their mass
A region in which a mass experiences a force
An attractive force between objects (dependent on their
mass)
The formation of points of reinforcement and cancellation
when two sets of waves overlap
When one variable is inversely proportional to the square
of another
Upside down
A region in the Earth’s atmosphere where ionisation
caused by incoming solar radiation affects the
transmission of radio waves; it extends from 70km to
400km above Earth.
Laser
Launch angle
Lens
Light sensitive chip
Line of sight
Magnification
Magnitude
Microwaves
Momentum
Noise
Normal
Optical fibres
Orbit
Parabolic
(in) Phase
Pixels
Polar orbit
Polarised light
Polaroid
Principle axis
Projectile
Projector
Source of intense, narrow beam of light. “Light
Amplification by Stimulated Emission of Radiation”
The angle at which a projectile is thrown
A piece of transparent material, often glass, that is fatter
in the middle than the ends (convex) or thinner in the
middle than at the ends (concave)
Surface in a digital camera that records light
electronically, producing a digital image
In direct line with no obstructions
The ratio of the height of the image to the height of the
object
Size of something
Non-ionising waves used in satellite and mobile phone
networks, as well as microwave ovens
The product of mass and velocity of an object.
Unwanted signals
A line perpendicular to a surface
Very thin glass fibres that light travels along by total
internal reflection (TIR)
The path taken by a satellite
Shaped like a parabola
When two waves are “in step” with each other; crests
coincide and troughs coincide
Short for picture elements; stores data in the lightsensitive chip of a digital camera
A satellite orbit that passes over Earth’s North and South
poles
Light in which the oscillations are confined to one plane
only.
A material that absorbs light except that polarised in one
particular plane, producing polarised light
The axis, perpendicular to the face of a lens, that passes
through the optical centre
Any object thrown in Earth’s gravitational field
An optical instrument that produces an enlarged image on
a screen
Radiowaves
Range
Reaction force
Real (image)
Receiver
Refraction
Refractive index
Reinforcement
Relative speed
Re-transmits
Ripple tank
Satellite
Scalar
Shutter
Total internal
reflection (TIR)
Trajectory
Transmitter
Troughs
Vector
Virtual image
Wavelength
Weight
Non-ionising waves used to broadcast radio and TV
programmes
The horizontal distance covered by an object
When an object feels a force it pushes back with an equal
reaction force in an opposite direction
An image that can be projected onto a screen; light
actually passes through it
Device which receives waves e.g. mobile phone
A change in speed, and usually direction, when light passes
from one medium to another e.g. from air to glass or water
The ratio of the speed of light in a vacuum (or air) to the
speed of light in a medium
When two waves combine to give increased amplitude;
constructive interference
The speed of a moving object with respect to another
Sends out a signal again (often after amplification)
Equipment containing a water surface to observe wave
motion
A body orbiting a larger body e.g. communication satellites
orbit the Earth
A quantity having magnitude but no direction
In a camera, it opens and closes very quickly to let light
into the camera
Complete reflection of a light ray within glass when the
ray hits the glass/air boundary at an angle which is
greater than the critical angle.
The path of a projectile
Device which transmits waves e.g. mobile-phone mast
Lowest points of a wave
A quantity having magnitude and direction
Image formed on the same side of the lens as the object;
a virtual image formed by reflection can be seen but
cannot be projected onto a screen.
Distance between two wave peaks
Force on an object due to gravitational attraction