Science Glossary
Physics - P3
Science Glossary
Physics Unit 3.1 – Medical applications of physics.
Key Word
Charge-coupled Device
(CCD)
Converging (Convex)
lens
CT Scan
Dioptre (D)
Diverging (Concave)
Lens
Far Point
Focal Length
Long Sight
Near Point
Power of a Lens
Definition
A device used to form digital images.
A lens that focuses parallel light rays onto a point.
Convex glasses are converging lenses.
Computed tomography scan, a series of x-ray pictures
combined into a 2D or 3D image by computer.
The unit used by opticians to measure the power of a
lens; 1D = 1 (focal length in m).
A lens that causes a beam of light to spread outwards
(diverge). Concave lenses are diverging lenses.
The furthest point at which an object can be seen
clearly; it is infinity for someone with perfect
eyesight.
The distance from the centre-line of a lens to its
principal focus; f.
Someone with long sight cannot focus on close
objects, either because their eyeballs are too short, or
the lenses are unable to become round enough to
focus.
The closest position at which an object can be seen
clearly. For a person with good eyesight the near
point is about 25cm from the eye.
1/ focal length, measured in Dioptres (D)
Principal Focus
The point at which parallel rays of light are brought
together on passing through a lens.
Range of Vision
The distance between the near point and the far point
for a person’s vision.
An image through which light rays pass so that it can
be seen on a screen placed at that point. It can be
projected
The change in direction of a wave as it goes through
Real Image
Refraction
Refractive Index
Short Sight
Snell’s Law
Ultrasound Waves
Virtual Image
an interface into a different material in which the
wave travels at a different speed.
An expression that describes the amount of bending
that takes place when light passes from one medium
to another. The refractive index = sin i/sin, r, where i
= angle of incidence and r = angle of refraction.
The inability of the eye to focus clearly on distant
objects.
The law of refraction
sin 𝑖
Refraction index, n =
sin 𝑟
Sound waves with a frequency above 20 000 Hz,
which is too high for the human ear to detect.
An image that light rays do not pass through; they
only appear to come from the image. They cannot be
projected onto a screen
Physics Unit 3.2 – Using physics to make things work.
Key Word
Amplitude
Centre of Mass
Centripetal Force
Effort
Equilibrium
Hydraulic Press
Line of Action
Load
Oscillation
Pascal (Pa)
Pivot
Pressure
Principal of moments
Resultant Moment
Time period
Definition
The maximum displacement of a particle as a wave
passes; half the height of the wave.
A point at which all the mass of an object appears to
act. The centre of mass of a hanging object will
always be directly below the point of suspension.
The force causing motion in a circle, acting towards
the centre of the circle
The force exerted on, for example, a lever.
When something is balanced, e.g. a seesaw is in
equilibrium when it is horizontal
A force multiplier that works by transferring a small
force on a small area via pressure in a fluid into a
large force on a large area
This goes from the centre of mass and follows gravity
going to straight downwards
The force exerted on one end of a lever.
Vibration or repetitive pattern of movement, for
example, up and down or side to side.
The standard unit for pressure.
The axis of rotation, the axis around which an object,
for example a lever, can rotate.
The force exerted divided by the area on which it is
exerted. Usually measured in pascals (Pa).
The sum of the anticlockwise moments equals the
sum of the clockwise moments
The overall moment acting on something
The time taken for one complete oscillation, for
example the swing of a pendulum or the passage of a
wave.