LEARN HOW YOUR
EYE WORKS...
USING JELL-O?@PopularMechanics _ March 2019 79IL
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YOU SEE THINGS—a tennis ball flying at your racket,
a lion at the zoo, a funny video—because your eye is
absorbing the light in front of it. All of that light goes
through a part of your eyeball right near the middle
called the lens, where it’s slowed down and bent in a process called refraction, then passed on to
the part of your eye called the retina. Your retina is at the back of the eye. It translates the light
into information your brain can understand, and your brain tells you what you’re seeing. Here’s a
fun experiment you can do with Jell-O that shows you how refraction works. It uses lasers, which
can be dangerous if you look directly at them, so get an adult to help you out.By iJus t i n e
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TOOLS AND
MATERIALS REQUIRED
1 box red Jell-O
2 or 3 red laser pointers
(available for $6 each on
Amazon). Note: It’s very
important that the laser
color matches the color of
your Jell-O. Otherwise the
light will not show up clearly.
1 sharp knife with a
smooth blade
1 square baking dish
1 round ice cube mold
(available for $7 on
Amazon)
Graph paper (optional)INSTRUCTIONS
Step 1: Mix the Jell-O
according to the box’s
instructions. Pour half into
a square pan and the other
half into your round mold.
Put into the fridge for two to
four hours to cool.
Step 2: Ta k e t h e J e l l - O f r o m
the pan and use the knife to
cut out a two-by-two-inch
square. Put it on a plate or a
piece of graph paper.
Step 3: Point the laser
so it hits the Jell-O at a
45-degree angle. What hap-
pens to the beam of light as
it passes through the Jell-O?
What if you change the angle
of the laser?Step 4: Cut the rest of the
Jell-O square up into differ-
ent shapes and notice how
the laser refracts differently
when it hits the new shapes.
Try shining two lasers into
the Jell-O from different
angles at the same time and
see what happens.
Step 5: Place the sphere of
Jell-O on a plate or a sheet
of graph paper. Shine one
laser through it. What hap-
pens to the beam of light?
Try it with two or three
lasers from different angles
at the same time.
Step 6: Eat the rest of the
Jell-O.Just like you would have
to walk more slowly to
get through deep snow,
light moves more slowly
through denser materi-
als. When the laser hits the
Jell-O, it slows down, shift-
ing its direction slightly and
bending the laser line. Because a sphere is perfectly
round, laser beams from
multiple angles will be shifted
to a single point. That’s exactly
what’s happening inside your
eye when light hits it!