1. LIGHT
What is light and why is it essential to life?
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2. What is light ?
Light is a form of energy. It can be changed
from one form of energy to another.
 For example, light entering your eye is changed to
chemical and electrical energy which is transmitted
to your brain.
Light energy can only be produced from other
forms of energy.
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3. Two types of light energy
Objects that
convert their
energy to produce
their own light are QuickTime™ and a
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LUMINOUS.
LUMINOUS
For example, some fish
living in the depths of the
ocean produce their own
light to attract prey.

4. Two types of light energy
NON LUMINOUS
objects do not give
off their own light,
they reflect light.
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For example you can see a
car because it is
reflecting light from the
sun.

5. But how does light travel?
- Ocean waves travel on the surface of the water. You can
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see them and you can feel them.
- Have you ever seen a flag on a windy day? The wind
creates waves in the flag.
- Sound is also a type of wave that we cannot see.
- Sound waves need something to travel through (like waves through
the ocean or wind through a flag). Sound can travel through air
because air is made of molecules. These molecules carry the sound
waves by bumping into each other, like dominoes knocking each other
over. Sound can travel through anything made of molecules - even
water!
- There is no sound in space because there are no molecules there to
transmit the sound waves.

6. All light has both particle-like
and wave-like properties.
Light is made of discrete QuickTime™ and a
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photons.
Photons travel at the speed of
light (300,000 km/s).

7. So light is a form of energy?
• White light is all colours, like the colours of the
rainbow.
• Sir Isaac Newton discovered the colour of light
by shining white light through a prism.
• This is called the "visible light spectrum."
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8. Light is energy
- Light is energy and there is energy beyond
visible light.
- The visible light spectrum is a part of a larger
spectrum called the:
Electromagnetic Spectrum.
Spectrum

9. ELECTROMAGNETIC ENERGY
When you tune your radio, watch TV, send a text message, or pop
popcorn in a microwave oven, you are using electromagnetic energy.
You depend on this energy every hour of every day. Without it, the world
you know could not exist.
Electromagnetic energy travels in waves and spans a broad spectrum
from very long radio waves to very short gamma rays. The human eye
can only detect only a small portion of this spectrum called visible light. A
radio detects a different portion of the spectrum, and an x-ray machine
uses yet another portion.
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10. OUR PROTECTIVE ATMOSPHERE
Our Sun is a source of energy across the full
spectrum, and its electromagnetic radiation
bombards our atmosphere constantly.
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However, the Earth's atmosphere protects
us from exposure to a range of higher
energy waves that can be harmful to life.
Exposure to Gamma rays, x-rays, and some
ultraviolet waves waves can alter atoms and
molecules and cause damage to cells in organic QuickTime™ and a
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These changes to cells can sometimes be helpful,
as when radiation is used to kill cancer cells, and
other times not, as when we get sunburned.

11. Beams of Light
Electromagnetic waves do not need molecules
to travel, unlike sound waves.
Electromagnetic waves can travel through air
and solid materials as well as empty space.
Light is an electromagnetic wave we can see.
This is why astronauts on spacewalks use radios to
communicate. Radio waves are one kind of
electromagnetic wave.

12. Rays of Light & reflections
A stream of light rays is called a ray of light.
Light can pass through some materials and it can also be
reflected by other materials.
TRANSPARENT TRANSLUCENT OPAQUE OBJECT
OBJECT OBJECT
Glass, clear water,
clear plastic cling Frosted glass or Wood, cement,
wrap. stained glass concrete
windows.

13. What is a shadow?
A shadow outlines the area where light cannot reach.
There are two types of shadows.
UMBRA SHADOW PENUMBRA SHADOW
This is a This is a semi shadow
complete shadow. with usually a fuzzy
Think of using a torch outline.
to make animal
shadows on a wall.

14. WAVESTOWN
This Doppler-radar
image seen on TV
weather news uses
microwaves for local
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Gamma Rays!!
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Imaging

15. Reflections & Plane Mirrors
One property of light is that it reflects off surfaces.
When you look at yourself in a plane mirror you see an image of
yourself.
The reflection in the mirror appears to
originate from inside the mirror at a
distance equal to the distance the
person is in front of the mirror.
Plane mirrors produce virtual, upright
images that are the same size as the
object and the same distance from the
surface of the mirror.

16. The law of reflection
When a ray of light strikes a plane mirror, the light ray reflects off the
mirror. Reflection involves a change in direction of the light ray.