SIGHT
Think of a
ll of the th
ings you
would find
it difficult
to
you could
not see. Yo do if
u
helps to m
ake lots of r sight
thin
do everyda
y much, mu gs you
ch easier.
Try to hold your head facing forward and look straight behind you.
Is it possible? Can you do it? The reason why you can't do this is
because your eyes are ball shaped, but all that can be seen is the
fronts of them. The rest of your eye sits inside your skull to protect it.
Your eyeballs fit nicely into two sockets in your skull – you can feel the
edges of these sockets if you touch lightly around the edges of your eyes.
Retina
Iris
Pupil
Now go into a room and
turn of the light. What
can you see? Very little at
all! Your eyes need light
to work. The light travels
through the black dot in the
middle of your eye, called
your pupil. The coloured ring
around your pupil is called
the iris.
Optical
nerve
The size of your pupil
decides how much light
gets let into your eye. When
there is too much light, like
on a sunny day, your pupil
goes small to stop too much
light getting in. When it is
darker, your pupil opens
big and wide to let as much
light in as possible. Test it
out – go into a dark room
with a mirror, and then turn
on the light. Watch as your
pupils shrink!
Your eyebrow
s are there to
stop
things falling do
wn off your
forehead into
your eyes, like
your
sweat. Your ey
elashes are th
ere
to stop things
going into your
eye,
they catch thin
gs when they ge
t
near to your ey
eball. Your eyel
ids
wipe tears acr
oss your eyes
every
time you blink
, keeping them
clean.
Your eyes work together to
help you understand how
near or far something is.
Throw a ball up into the air
and try to catch it, and then
try to do the same thing
with one eye shut.
It is much harder!
SPARK
9