1. YR9 Science: Light Properties of light Reflection Colours Refraction
Eye structure

2. When light rays hit the surface of an object..
The light energy is absorbed and changed into heat energy.
The light bounces off the surface of the object and is reflected.
The light travels through the object but the ray is bent or refracted as it passes through.

3. Part 1 – Properties of Light
Light travels in straight lines:
Laser

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

5. 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.

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

7. Luminous and non-luminous objects
A luminous object is one that produces light.
A non-luminous object is one that reflects light.
Luminous objects
Reflectors

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

9. Properties of Light summary
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

10. Part 2 - Reflection Reflection from a mirror: Mirror Normal
Incident ray
Reflected ray
Angle of incidence
Angle of reflection
Mirror

11. Angle of incidence = Angle of reflection
The Law of Reflection
Angle of incidence = Angle of reflection
In other words, light gets reflected from a surface at ____ _____ angle it hits it.
The same !!!

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. Plane (flat) mirror Reflection

14. Lots of spectacular and beautiful effects are caused by the reflection of light.
Reflections occur when light bounces off the surface of water or some other smooth surface into your eyes.

15. Reflection of light
If a surface is uneven, rough or dull such as paper or cloth, light rays are scattered in different directions and a clear picture will not form.
This is called diffuse reflection.

18. Reflection of light
1. List three characteristics that a surface would have if it was a high quality, regular reflector of light.
2. List three characteristics that a surface would have if it was a diffuse reflector of light.

19. Smooth, shiny, even surface Uneven, rough or dull surface
Reflection of light
1. List three characteristics that a surface would have if it was a high quality, regular reflector of light.
2. List three characteristics that a surface would have if it was a diffuse reflector of light.
Smooth, shiny, even surface
Uneven, rough or dull surface

20. Look larger, unfocused, upside down.
Reflection and light
There are 3 types of mirrors and they can produce difference of objects.
Plane mirror
Concave mirror
Convex mirror
Flat, shiny surface.
Curved,
Reflecting side
“caving inwards”
Look larger, unfocused, upside down.
“flexing outwards”
Look sharp and small.

21. An image is picture of an object produced by a mirror.
Reflection and light
An image is picture of an object produced by a mirror.
Images can appear to be similar or different to the actual object.

22. Virtual image in a mirror
An image in a plane mirror appears to be behind the mirror. = VIRTUAL IMAGE
The light rays coming off the object do not pass through the reflecting surface, they bounce off.

24. USING A LIGHT RAY BOX

25. normal
mirror

26. normal
Angle of
incidence
mirror
Draw a line

27. The laws of reflection
A ray of light striking a mirror is reflected as shown in the diagram

28. The laws of reflection Term Definition Angle of incidence
The angle between the ray of light that hits the mirror and the normal.
Angle of reflection
The angle between the ray of light that is reflected off the mirror and the normal.
Incident ray
The ray shinning onto the mirror.
Reflected ray
The ray that bounces off the mirror.
Normal
A line that is drawn at right angle(90°) to the mirror.

29. Angle of Incidence
Angle of Reflection
20°
40°
60°
80°

30. The angle of incidence is equal to the angle of reflection.
If the angle of incidence and the angle of reflection are measured using a protractor then we will always find that:
ANGLE OF INCIDENCE = ANGLE OF REFLECTION
The angle of incidence is equal to the angle of reflection.

33. Using mirrors
Two examples:
2) A car headlight
1) A periscope

34. Colour
White light is not a single colour; it is made up of a mixture of the seven colours of the rainbow.
We can demonstrate this by splitting white light with a prism:
This is how rainbows are formed: sunlight is “split up” by raindrops.

35. The colours of the rainbow:
Red
Orange
Yellow
Green
Blue
Indigo
Violet

36. Adding colours
White light can be split up to make separate colours. These colours can be added together again.
The primary colours of light are red, blue and green:
Adding blue and red makes magenta (purple)
Adding blue and green makes cyan (light blue)
Adding red and green makes yellow
Adding all three makes white again

37. Revise
Blue + red 
Red + green 
Green + blue 
Blue + green + red 

38. Blue + red  magenta
Red + green yellow
Green + blue cyan
Blue + green + red white

39. Only red light is reflected
Seeing colour
The colour an object appears depends on the colours of light it reflects.
For example, a red book only reflects red light:
Homework
White
light
Only red light is reflected

40. A white hat would reflect all seven colours:
A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and blue):
Purple light
A white hat would reflect all seven colours:
White
light

41. Using coloured light
If we look at a coloured object in coloured light we see something different. For example, consider a football kit:
Shirt looks red
White
light
Shorts look blue

42. In different colours of light this kit would look different:
Red
light
Shirt looks red
Shorts look black
Shirt looks black
Blue
light
Shorts look blue

43. Some further examples:
Object
Colour of light
Colour object seems to be
Red socks
Red
Blue
Black
Green
Blue teddy
Green camel
Magenta book
Homework

44. Using filters Red Filter
Filters can be used to “block” out different colours of light:
Red Filter
Magenta Filter

45. Investigating filters
Colour of filter
Colours that could be “seen”
Red
Green
Blue
Cyan
Magenta
Yellow

46. Red
Blue
Green
White
Yellow
Cyan
Magenta

47. Words – speed up, water, air, bent
Refraction
Refraction is when waves ____ __ or slow down due to travelling in a different _________. A medium is something that waves will travel through. When a pen is placed in water it looks like this:
In this case the light rays are slowed down by the water and are _____, causing the pen to look odd. The two mediums in this example are ______ and _______.
Words – speed up, water, air, bent

50. Structure and Function of the Human Eye

55. Human Eye vs. Camera A human eyeball is like a simple camera!
Sclera: outer walls, hard, like a light-tight box.
Cornea and crystalline lens (eyelens): the two lens system.
Retina: at the back of eyeball, like the film.
Iris: like diaphragms or stop in a camera.
Pupil: camera aperture.
Eyelid: lens cover.