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LIGHT

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by

Carolina Bautista

on 6 April 2014

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Transcript of LIGHT

LIGHT

Dispersion of light
Reflection of Light
When light hits an opaque object, it bounces off, just like a tennis ball bouncing off a racket. This is called
reflection
. Reflected light allows us to see objects.

Most objects only reflect part of the light that hits their surface. However, a
mirror
reflects all the light. This is why you can see an image of yourself in a mirror
When light rays reach an object, this object
absorbs
some of the light and
reflects
some of it. The reflected light enters our eyes.

An object always reflects its own colour. For example, a red bicycle reflects red light. It absorbs blue, magenta, white, yellow, green and cyan.

White objects reflect all light. This means they do not absorb any light.

Black objects absorb all light, This means they do not reflect any light.
In Ireland it rains a lot. When it rains and the Sun shines at the same time, rainbows appear in the sky. A rainbow is a huge arc of many colours.
A little about Ireland
The Irish people have a legend: they say that at the end of every rainbow there is a pot of gold. A magical little man, called a
leprechaun
, guards the gold.
Light Travels
When we switch on a light bulb, light travels to every corner of the room.
Light travels in all directions
at a speed of 300,000 kilometres per second. This is so fast that we cannot see light moving.

Light travels in a straight line
, so it cannot move around objects. This is why we see shadows.
Light and Objects
There are three different types of objects, according to how much light passes through them.
Transparent Objects
Light can pass easily through transparent objects. When you look through them, you see light, as well as objects on the other side.
Clear plastic
Clean Water
Clear Glass
Air
Translucent Objects
Only some light can pass through translucent objects. When you look through them, you see blurred objects on the other side.
Tissue Paper
Bubble Wrap
Ice Cubes
Dirty Water
Opaque Objects
Light cannot pass through opaque objects. a shadow forms on the other side.
Wood
Stone
Cardboard
Aluminium
LIGHT
The reflection of light
Light hits an object. The object reflects the light. The reflected light enters your eyes.
Refraction of light
Light
bends
and changes direction when it passes from one transparent
medium
to another. This is
refraction
. Water, clear glass, lenses and air refract light.
In the photograph, a ray of light bends as it passes from the air to a glass prism. A prism is a solid, transparent object. The light bends again as it passes from the prism to the air.
Another example of refraction
If you put a pencil in a glass of water, it looks bent. This is because light is refracted when it passes from the water.
Lenses
are transparent objects made of glass. Lenses refract light. They can be
convex
or
concave
, as in the diagrams.
Sir Isaac Newton discovered that
white light
(sunlight) is made up of many colours.

He did an experiment with a triangular prism. A prism separates light into the seven colours of the rainbow:
red
,
orange
,
yellow
,
green
,
blue
,
indigo
and
violet
.
When the Sun shines and it rains at the same time, we see a rainbow. This is because the raindrops act like tiny prisms: they separate the white light into the seven colours of the rainbow.

We say that prisms
disperse
white light into all colours.
Primary Colours of Light
The primary colours of light are
red
,
green
and
blue
. When we mix the primary colours of light, we create new colours.
For example, when we mix red light with green light, we create yellow light. When we combine the three primary colours of light, we create white light.
The primary colours are:
and
Mix colours
Reflection or Refraction
Occurs when light bounces off an object

QUESTIONS
occurs when light is bent
The path of light through a concave lens is:

- not directed to a single focal point

- directed to a single focal point
The path of light through a convex lens is:

- not directed to a single focal point

- directed to a single focal point
Blue ball
Red ball
White ball
Black ball
Reflects

blue light

and
absorbs
red, magenta, white, yellow, green and cyan.
Reflects

red light

and
absorbs
blue, magenta, white, yellow, green and cyan.
Reflects

all light
and it doesn't
absorb

any light
Absorbs

all light
and it doesn't
reflect

any light
.
Full transcript