Elenco LIGHT - Manual (Page 11)

Light in Our World
-10-
What would our world be like without light?
Moving and doing things in total darkness
would be much more difficult, because
everyone would be blind. Plants rely on
sunlight for energy and would die without it. If
all the plants die, then people and animals
would have nothing to eat, and would starve.
Let’s hope we never have to live in a world
without light.
Light is energy, traveling at high speed.
Sunlight can warm up your skin, as can bright
lights in a concert hall or playhouse. Light can
carry information. For example, our brains
analyze the light received in our eyes, to learn
what is around us. In fiber optic cables, beams
of light carry data between cities. Infrared light
from a remote control can tell a TV to change
to a different channel.
Light moves as super-tiny charges, which are
so full of energy they go flying off in all
directions.
This happens when a material has too much
energy, and some of the energy changes form.
For example, a light bulb makes light when an
electric current makes the filament so hot that
it glows. Some of the energy in a burning fire
escapes by changing to light. Our bright sun
makes so much light because it is basically a
gigantic ball of thermonuclear reactions. Light
emitting diodes (LEDs) make light by
converting excess electrical energy.
You “see” when light enters your eyes. When
you turn on a light in a room, the light shines
on everything around it. When light shines on
something, some of the light is absorbed into
it, and the rest is reflected off. The absorbed
light is converted to heat, and the reflected
light is scattered around the room. Some of the
shining and reflected light might reach your
eyes. Your brain interprets the light into your
eyes, and makes the mental picture you see.
When all the light shining on something is
absorbed, with none reflected towards your
eyes, then you can’t see it. The object will
appear dark. The brighter an object appears,
the more light was reflected off it and into your
eyes. Some materials, like air and clear glass,
let light pass through them.
You can only see the
moon when light from the
sun bounces off it, and
reflects to earth.
You can’t see a beam of light traveling across
a room, unless something scatters the light
and some reaches your eyes. In a dusty room,
sometimes you can see the dust particles
floating in the air when sunlight hits them.
In this photograph,
sand has been
tossed into the air,
which is illuminated
by a narrow beam of
sunlight coming down
into the canyon.
When you turn on a
light, you instantly
see everything. This
happens because
light is very fast, and
travels about 186,000
miles a second in air.
Light rays can bend when they pass between
different materials, such as air and water. Light
bends because its speed changes. The speed
of light in water is only about 125,000 miles a
second.
The part of the pen in water
looks distorted, because light
changes speed when entering
and leaving the water.
When you look directly out a
glass window, you can see
clearly through it. When you
look through the window at a
wide angle, you can see
through it, but also see a reflection in it. When
you try to look through the window at a really
wide angle, you can’t see through it at all, and
only see reflections. Try looking through a
window in your home at really wide angles.
Light bulb
filament
Glowing
light bulb
filament
Close-up
view of the
Sun
Glowing
white LED
(D6)
White light beam
Reflected light
Mental picture