Childrens Illustrated Encyclopedia

light

316

Fiber optics

Fiber optic cables are channels that carry light. They

are flexible, so they can carry light around corners.

The fibers are long, thin filaments of glass; the light

bounces back and forth along the inner surface of the

glass. Fiber optics are valuable for seeing into awkward

places. Doctors can use fiber-optic endoscopes to see

inside a patient’s body without opening the body up.

Convex mirror

produces images

smaller than

the object.

Magnifying

glasses are

convex lenses.

Light refracts when it passes

through water, because the water

slows it down. This makes objects

look as though they are bent.

Mirrors

Light passes easily through

transparent substances, such

as glass and water, but not

through opaque objects,

such as paper. Most opaque

objects have a rough surface

that scatters light in all

directions. However, a

mirror has a smooth surface,

so it reflects light in a regular

way. When you look at your

face in a mirror, the light

bounces straight back,

producing a sharp image.

Most mirrors are made of

glass; your face is reflected

from a shiny metal coating

at the back of the mirror,

not from the glass.

Convex

Mirror

Mirrors that bulge

outward are called

convex mirrors.

Their curved shape

reflects light from

a wide angle, giving a much wider view

than a regular mirror does. This has the

effect of making all objects look small.

Lenses anD reFraCTion

Glasses, cameras,

telescopes, and

microscopes use lenses to

create particular kinds of

images. The lenses in a

telescope, for example,

produce a magnified view

of a distant object. all

lenses work on the

principle that although

light always travels in

straight lines, it travels

slower through glass than

through air. if a light ray

strikes glass at an angle,

one side of the ray will hit

the glass just before the

other, and will slow down

earlier. The effect is to

bend the light ray slightly,

just as a car pulls to one

side if it has a flat tire.

This bending of light

is called refraction.

ConCave Mirror

a concave mirror, which is curved

inward, forms two kinds of images.

if the object is close to the mirror, the

reflection is larger than the real thing.

if the object is far away, the image

formed is small and upside down.

PLane

Mirror

With a plane,

or flat, mirror,

the reflection is

exactly the same

size as the object,

but the left and right are reversed. With

both curved and plane mirrors, the

reflection appears as though it were

behind the mirror.

Concave

mirror

produces a

magnified

image.

A flat mirror produces

an image the same

size as the object.

ConCave Lens

a concave lens is thicker at the

edges than in the center, so it

spreads light rays out. if you look

through a concave lens, everything

appears smaller.

Focus

Convex Lens

Convex lenses bring light rays

together. at the focus, where light

rays from a distant object meet, they

form an image of the object that

can be seen on a screen.

Find out more

Cameras

Color

eyes

Photography

Physics

Plants

sun

MiraGe

in the hot desert, weary travelers are often fooled by the sight of an oasis.

The oasis appears on the horizon, only to vanish as the travelers hurry

toward it. What they have seen is an illusion called a mirage. in the example

above, light rays traveling from the palm tree are bent upward by the warm

air. The observer’s eyes interpret the light as having traveled in a straight

line, so he or she sees a watery reflection of the tree on the ground.

Upside-

down image

forms

Rays travel in straight

lines in cool air

Rays are bent

as they pass

through layer

of warm air

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