3. • How can we see?
• We need light for vision.
• How can we see an object ?
• Light falls on an object . Then it get reflect and reached to our eye . Then
see an object.
vision
3
4. Whether light is needed for vision
• Needed things : A cardboard box, A scissor,1 50 cent coin , 1 1 rupee coin , small
object
Method :1. get a cardboard box
2. Make a hole of the center of the lid about a 50 cent coin .
3.Make another hole of the side of the cardboard box .
4.put 1 rupee coin on the center of the lid .
5.ask 1 friend to see the things inside the box by looking through the side
hole .
6.remove the 1 rupee coin and ask him again
• Observation : Friend said he could not see clearly when 1 rupee coin on the hole.
• Later he said correctly the object was in the box , when remove the coin
and lighted .
• conclusion : light is needed for vision 4
5. Sources of light
• The object which produce light is called as a source of light .
sun is the main sources of light
Star
5
6. • Other sources of light
Living things
Artificial light sources
Candle
Flash
light
Fluorescent
Jelly fish
Firefly
Natural light sources
6
7. 1.How to draw a light ray
• Light ray should be straight .
• The arrow head should represent the way that light travels.
Light rays
7
8. A light beam
Drawing a light beam.
A collection of light rays form of a light beam .
All the light rays should be parallel to each other
the arrow head should be marked each of light rays
8
9. • Does light travel in a straight line?
• Conclusion: light travels in straight line
9
10. The materials based on passing
the light rays
• Transparent materials - the materials which allow light to pass through
them.
• Transluscent materials - the material which allow light to pass partially.
• Opaque materials - the materials which do not allow light to pass
through them.
the materials that can absorbed or reflected the
light.
10
11. Transparent materials
• The materials which allow light to pass through them.
• Examples : glasses , colorless polythene , pure water
11
12. Transluscent materials
• The materials which allow the light to pass partially .
• Examples : decorated glasses, colored polythene , plastic cups
12
13. Opaque materials
• The materials which do not allow light to pass through them. The
materials that can absorbed or reflected the light.
• Examples : apple , a sofa , orange
13
14. Uses of light
1.In medical field
2.For photosynthesis
3.To give signals
4.For entertainment
5.For communication 14
15. 1.Uses of light in medical field
• Head Mirror
• Otoscope
•
• Phoropter
15
