physical science

1. Light

2. Light energy
• Light is a small part of a range of
spectrum called { Electromagnetic
spectrum }
• It doesn’t need a medium to travel through
{ Unlike the sound energy}
• Light travels in a wave called : Transverse
wave

3. As light hits an object light is
either:
• Absorbed
• Reflected
• passed

4. Where does light come from?
Our major
light source:
the Sun

5. Where else does light come from?

6. Sorting light sources
Natural vs. Man-made (artificial)

7. Are these light sources?
moon
water
mirror
These items are not light sources, instead they
are reflecting light from other sources.

8. Light can travel through vacuum.
Speed of light in vacuum is faster than its speed in solid, liquid or gas.

9. How does light travel?
Light rays travel in straight lines from the light source.
When it hits an opaque object, some light is absorbed and
the rest reflects off.
If the object is transparent, light rays pass through it
easily.
If the object is translucent, some light can pass through,
but the rest of the light will be reflected.
light
source

10. Types of materials
Transparent
Translucent
Opaque
Allow most light to
pass through them.
Allow some light to
pass through them.
No light can pass
through them.

11. How do we see colour?
light
source
 Light from most light
sources looks white, but
actually contains all the
colours of the spectrum;
also known as the
rainbow.
 If an object looks blue, it
is absorbing every colour
except blue, which is
reflecting off it and
entering your eyes.
 If an object looks orange,
it is absorbing every colour
except orange, which,
again, is reflecting off and
entering your eyes.
 If an object looks red...
(You get the idea!)

12. How does light reflect?
Angle of incidence
Angle of reflection
The ‘angle of
reflection’ is
always equal to
the ‘angel of
incidence’.
on
off

13. Light can only be reflected
in straight lines.
on
off

14. How does light form shadows?
Light rays travel in straight lines, radiating out from the
light source.
If rays are blocked by an opaque object a shadow forms
where the light cannot reach.
If the light source is moved closer to the object, more
light is blocked and a larger shadow is formed.
light
source
light
source

15. To change the size of the shadow, move closer or away
from the light source.

16. Look at the spoon in the glass of water.
Is the spoon broken?

17. The spoon is not broken.
When light enters a different medium it
bends and when it is leaving it bends to the
opposite side again.

18. Bending of light while passing from on
substance to another is called
REFRACTION.

20. Draw the light rays to explain what
is happening.