1. In this Unit you will learn:
Light
In this Unit you will learn:
Light is form of energy
Properties of light
Laws of reflection reflection
Understand how to locate an image by no parallax
Lateral inversion
How images are formed in plane mirrors
Uses of plane mirrors

2. Keywords
reflection
No parallax
normal
Light ray
Diffuse reflection
Regular reflection
luminous
non-luminous
Ange of incidence
Angle of reflection
Reflected ray
Incident ray
Virtual image
Converging ray
Diverging ray
Energy
Lateral inversion
periscope

3. Light is form of energy Light can do work eg. Crookes radiometer
Light can be converted to other forms of energy e.g. Solar cell, light to electricity. (show demo model of this)
Other forms of energy can be converted to light e.g. Fire.

4. Part 2 – Properties of Light
Light travels in straight lines:
Laser

5. Light travels VERY FAST – around 300,000 kilometres per second.
At this speed it can go around the world 8 times in one second.

6. Light travels much faster than sound. For example:
Thunder and lightning start at the same time, but we will see the lightning first.
2) When a starting pistol is fired we see the smoke first and then hear the bang.

7. We see things because they reflect light into our eyes:
Homework

8. Luminous and non-luminous objects
A luminous object is one that produces light.
A non-luminous object is one that reflects light.
Name 3 luminous sources of light and 3 reflectors
Luminous objects
Reflectors

9. Shadows
Shadows are places where light is “blocked”:
Rays of light

10. Properties of Light summary
Light is a form of energy
Light travels in straight lines
Light travels much faster than sound
We see things because they reflect light into our eyes
Shadows are formed when light is blocked by an object

11. Reflection The bouncing of light of an object is called reflection
A straight líne showing the direction in which the light is travelling is called a light ray
Beams of light can be coverging, diverging or parallel.

12. Clear vs. Diffuse Reflection
Smooth, shiny surfaces have a clear reflection:
Rough, dull surfaces have a diffuse reflection.
Diffuse reflection is when light is scattered in different directions

13. Reflection Reflection from a plane mirror: Mirror Normal
Incident ray
Reflected ray
Angle of incidence
Angle of reflection
Mirror

14. The Laws of Reflection
Incident ray, reflected ray and normal lie on the same plane
Angle of incidence = Angle of reflection
In other words, light gets reflected (bounced) from a surface at ____ _____ angle it hits it.
The same !!!
Normal

15. How an Image is formed in a plane mirror
The image is located ón the perpendicular form the object to the mirror.
The image is the sames distance behind the mirror as the object is in front of the mirror.

16. Experiments
To demonstrate the laws of reflection using a plane mirror.
To locate an image in a plane mirror the method of no parallax

17. Lateral Inversion
Lateral inversion is where the left of an object appears to the right
image and vice versa.

18. Real and Virtual images
A virtual image is an image formed by th apparent intersection of light rays.

19. Use of plane mirrors Two examples: 2) looking at yourself
1) A periscope

20. Using no parallax to find an image
The apparent relative motion of the two pencils due to the motion of the observer is called parallax
In diagram (b) there is not apparent relative motion of the pencils due to the motion of the observer, this is called no parallax