2.  Light is a form of energy.
 We can see objects because they reflect
light.
 They can be natural or artificial.

3.  The Sun is a source of natural light.
 A light bulb is a source of artificial light.

4.  Light travels in straight lines and in all
directions from the source of light.
 Light travels very quickly, at 300,000
kilometres per seconds.

5.  Light passes through transparent materials.
 Only part of the light passes through
translucent materials. Light rays separate
into different directions.
 Light does not pass through opaque
materials.

6.  Reflection lets us see objects that do not
emit light. When light reaches an opaque
object, it hits the object and light changes
its direction. It reflects the light.
When we look in a mirror, we see our
reflection in it because light rays do not
separate.

7.  When a ray of light goes from air to water, its
speed changes. As a result, the ray changes
its path. This is called refraction.
o When white light passes through a drop of
rain, the ray of light refrects. Each ray of
colours separates, forming a rainbow.
o Light also refracts when its passes through a
lens. There are two tipes of lenses, coverging
and diverging.

9.  Glasses and contact lenses.
 Projectors:
 Telescopes and binoculars.
 Magnifying glasses and microscopes.

11.  Sound is a form of energy produced by
vibrations.Our vocal cords vibrate and create
our voices.

12.  Intensity. Sounds can be soft or loud.
 Pitch can be high or low.
 Timbre is the quality of a sound.

13.  Sound travels in all directions and In straight
line.
 Sound is slower than light.It travels at 340
metres por second.

14.  When the sound waves reach an
obstacle,they reflect in two different ways:
 Echo happens when the obstancle is more
than 17 metres away.
 Reverberation happens when the obstacle is
a shoter distance away.The reflected sound
mixes with the emitted sound.