Waves can travel through water; the water
rises and falls but the wave moves on. This is a
wave.
Water waves can be reflected.
If two sets of waves meet they can add to each other
or cancel each other out.
of
the wave
water level when direction of travel of the wave
the water is calm
of
the wave
the water goes up and down as the wave passes through
Sound waves are
waves. The wave
travels in a direction parallel to the
of the material that the wave is travelling through.
Sound waves can vary in frequency, which is
measured in
. Sound waves can be
reflected (an echo) or absorbed.
Key vocabulary
amplitude
the maximum displacement
of a point on a wave from its
undisturbed position
auditory
range
the range of sound frequencies
from the lowest to the highest
that an animal or human can
hear
echo
the reflection of a sound wave
from a surface
frequency
number of waves that pass a
point, or are emitted, in one
second; unit hertz (Hz)
hertz (Hz)
unit of frequency; equal to one
wave per second
longitudinal
wave
a wave in which the vibrations
are parallel to the direction of
energy transfer
loudspeaker
microphone
Waves carry energy
from one place to
another. The energy
transferred by
ultrasound waves can
be used to clean objects
and for physiotherapy.
Sound waves need
a medium to travel
through so it cannot
travel through a
vacuum. Sound travels
faster in
than in
, and it travels
slowest in
.
The range of frequencies that humans or animals can
hear is known as the
. This range is
different for different animals.
Sound is produced by objects vibrating, such as
the flexible cone in a loudspeaker. Sound is
detected as the effect on, for example, eardrums and
microphones, of vibrations sent through the air.
The energy transferred by sound waves is converted
by a microphone to an electrical signal carrying
information about the sound.
oscilloscope
apparatus that converts electrical
impulses into sound waves
Each colour of light has its
own range of frequencies.
White light is a mixture of
different colours, which
can be separated by a
triangular prism.
white light
enters the prism
prism
a device for changing effect of
vibrations from sound waves
into electrical signals
a device that allows sound
waves that have been turned
into electrical signals to be
viewed as waveforms
pitch
how high or low the frequency
of a sound is
reflection
when a wave, such as a sound
or light wave, bounces off a
surface
superposition
when two waves meet each
other at the same point
transverse
wave
wave in which oscillations are
at right angles to direction of
energy transfer
ultrasound
sound with a frequency higher
than 20 000 Hz
wavelength
distance along a wave from one
point to the next corresponding
point where the wave motion
begins to repeat itself – for
example crest to crest
vacuum
Light can travel through some materials but it may
also be absorbed, scattered or reflected.
a space where there are no
particles of matter
The speed of
light is much
than
the speed of
sound.
Key vocabulary
Objects look coloured
because
.
The absorption of
light as energy is how
light is detected by
a camera or by the
light-sensitive cells on
the retina of the eye.
Some electrical
devices can detect
light by producing
an electrical current
when energy from
light is absorbed.
A key difference between light
waves and sound waves is that
light does not need a medium to
travel through. Light waves can
travel through a
.
Ray diagrams show
how light is reflected
by a mirror, and how
a pinhole camera
forms an image.
incident ray
refraction happens at
both sides of the lens
angle of
reflection
the angle between the normal
and the reflected ray
convex lens
a lens that is thicker in the
middle and bends light rays
towards each other
concave
lens
a lens that is thinner in the
middle and spreads out light rays
image
the picture of an object that we
see in a mirror or through a lens
or system of lenses
lens
a specially shaped piece of
transparent material that refracts
light passing through it to form
an image
normal
a line at right angles to a surface,
from which angles of reflection
or refraction are measured
opaque
material that allows no light to
pass through
prism
(triangular)
a three-dimensional shape with
five flat faces, two of which are
triangles and the other three of
which are rectangles
ray
a line with an arrow to show
how a light wave travels as it is
reflected off a mirror or passes
through a transparent material
refraction
a change in the direction of a
wave such as light when it hits a
boundary between two different
media at an angle, for example,
when a light ray passes from air
into a glass block
retina
a layer at the back of the eye
with light-detecting cells, where
an image is formed
scattering
when light from a particular
direction reflects from a rough
surface in all directions
spectrum
a continuous range of values of
frequencies or wavelengths, for
example in the visible spectrum
of light
translucent
a material that lets some but not
all light pass through
transparent
a material that allows light to
pass through
reflected ray
Light can be refracted through
and
.
Ray diagrams show how light is refracted, including in
the eye.
object
the angle between the normal
and the incident ray
normal
angle of angle of
mirror
the cornea refracts light
angle of
incidence
image formed
on the retina
(upside down)
optic nerve