Slide that I created to support teaching science to my lower secondary student (Grade 7). The topic is Ray Model of Light. Some contents (pics and videos) are not mine. Hope it is useful for all teacher around the globe.

1. By Suta Pinatih
Secondary Level Science
2014
Ray Model of Light

2. What is light? How does it travel?
What happened when light is blocked?
Why do the leaves look green in the day and almost
black when there‟s no light?

3. Where does light come from?

4. Sun is our major light source!

5.  If there‟s no light, we would be in the darkness.
 Light is form of energy. It has no mass and
cannot be stored in a container.
 Light travels in a straight lines unless changes
what it travels through.
 Light travels through matter: gases (air), liquids
(water) and solid (glass).
 Sunlight travels a distance of 150 million
kilometres before reaching the earth.
Facts about lights

6. Are these light sources?
Moon Water Mirror
No, they aren‟t light sources. Because those objects do
not emit light from itself but they reflect off the light
from other light sources.

7. How do we see?
See the interactive content

8. Rays
 A thin line of light coming from a source is
called a light ray.

9. Beams
 A bundle of light rays is called a beam of
light. A beam of light can be parallel,
divergent or convergent.

10. 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

11. CLEAR=TRANSPARENT
SMOKY=TRANSLUCENT
SOLID=OPAQUE

12. How are shadows formed?
 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

13. How does sunlight cause
shadows?
6am
8am
9am
12am
2pm 10am
3pm
4pm
7pm
Looking North,
the Sun appears
to rise in the
East...
...and travel across
the sky until it sets
in the West.
The position of the
Sun effects the
position and length of
the shadows created.
Thanks to this natural
phenomenon a sundial
is able to tell us the
time, as long as it is a
sunny day!

15. Phases of the
moon.

16. Mid-autumn festival is celebrated on the 15th of the 8th month in
the Chinese calendar (full moon).

17. Hari Raya Idulfitri is celebrated at the end of Ramadan, marked by the
appearance of new moon on the last evening of Ramadan.

18. Solar eclipse
The moon blocks the light
from the sun
An observer on the earth
will experience total
darkness
The shadow of the moon is
formed on the earth.

19. Key Ideas
1. Light travels in a straight lines.
2. In the ray model of light, straight
lines with arrows are drawn to
represent the path of light rays.
3. Shadows are formed when light is
blocked by an opaque object.

20. Reflection of Light

21. How the light is reflected?
i= angle of incidence
r = angle of reflection
normal
Flat mirror
 The incident ray, reflected ray and the
normal at the point of incidence all lie in the
same plane.
 The „angle of reflection‟ is always equal to
the „angel of incidence‟ (i = r).

22. The texture of the surface affects the type of
reflection that occurs at the surface.
regular reflection
(Specular)
irregular reflection
(Difuse)

23. Have ever cut your hair in barbershop?

24. Plane mirror
b a
The images formed by a plane mirror are upright, same size
(undistorted), virtual and laterally inverted.

27. Plane mirror
dance studio
room looks larger

28. Periscope
Periscope is
used to change
the direction of
light by
reflection.

29. Concave mirror
 The shape bends inwards.
 The images formed by
concave mirror are virtual
and magnified if the object
is put near the mirror.

30. The uses of
concave mirror

31. Concave Mirror used in
Reflecting Telescope
http://www.bro.lsu.edu/telescope/Classroom/2.How%20Telescopes%20Work/Reflecting.gif

33. Concentrate Solar Power on Youtube

34. Convex mirror
 The shape bends outwards.
 Cover wider field of vision.
 The images formed by
convex mirror are upright,
distorted, laterally inverted
and smaller than the
object.

35. The uses of convex mirror

36. The word “AMBULANCE” is written laterally
inverted at the front of an ambulance.
Source: http://brighteststar.org.uk/wp-content/uploads/2013/02/hi-res-ambulance.jpg

37. Key Ideas
1. Reflection is the bouncing of light off the surface. Regular
reflection occurs at the smooth surface while irregular
reflection occurs at rough surface.
2. We use the ray model of light to represent the path taken
by light as it is reflected off a surface.
3. Plane mirror has flat surface. The image formed is
upright, laterally inverted, virtual and the same size as
the object.
4. A concave mirror has a surface that bends inwards. The
image formed is virtual and magnified.
5. A convex mirror has a surface that bends outwards. The
image formed is upright, distorted and smaller.
6. Different types of reflecting surfaces are used for
different purposes.

38. Concave & Convex Mirror
https://www.youtube.com/watch?v=jtTBOMVMSYM
Workbook Vol A
Worksheet 9.1

39. Refraction
Refraction is the bending of light as it travels
from one medium to another medium of
different density.
A
B
glass block

40. Refraction phenomenon
Source: http://upload.wikimedia.org/wikipedia/commons/b/b9/Refraction-with-soda-straw.jpg
http://media.digitalcameraworld.com/files/2012/10/Photography_effects_bending_light_refraction_NIK12.zone_4.refraction.jpg

41. Apparent Depth (an effect of refraction)

42. Key Ideas
1. Refraction is the bending of light as
it travels through one medium to
another of a different density.
2. The ray model of light can be used to
show the refraction of light.
3. Object in water appear closer to the
surface than they really are. This is
due to the refraction of light.

43. Dispersion of Light
1. When a beam of white light travels through
a prism, it is split into different colours.
2. This is because the different colours of
white light bend or are refracted towards
the normal through different angles. This
occurs when the beam of white light enters
and leaves the prism.
3. A spectrum of seven colours is produced.
This splitting of white light is called
dispersion.

45. Key Ideas
1. The dispersion of
white light is the
splitting up of white
light into its
component colours.
2. The different colours in white light
are refracted through different angles
by a glass prism. This results in the
dispersion of white light.

46. Colours
White light is made up of seven different
colours (Red, Orange, Yellow, Green, Blue,
Indigo, Violet).
We classify these colours as
primary and secondary
colours.
Primary colours are basic colours that can not be obtained by
mixing other colours together. Primary colours are: red, green,
blue.
Secondary colours are formed by mixing primary clours.
Secondary colours are: cyan, yellow, magenta.

47. Colours

48. 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!)

49. Key Ideas
1. Red, green, blue are primary colours
of light which can be mixed to form
the secondary colours of light : cyan,
yellow and magenta.
2. The colour of an object depends on
the type of coloured light that is
reflected off its surface.

51. Resources
Joan Fong. Lower Secondary Science Matters Volume B Second Edition. Marshall Cavendish.
http://www.childrensuniversity.manchester.ac.uk/interactives/science/brainandsenses/eye/
http://www.cyh.com/HealthTopics/HealthTopicDetailsKids.aspx?p=335&np=152&id=1730
Pictures Credits
http://photos1.blogger.com/blogger/5361/1488/1600/forest1.0.jpg
https://encrypted-
tbn2.gstatic.com/images?q=tbn:ANd9GcT9SJp0ro8CgVLYTnb4bytGF7cxFoPptNy
QeWRdZzblfN8lbYh1
http://hqwide.com/wallpapers/l/1366x768/22/landscapes_night_stars_galaxies_
guy_torch_flashlight_beam_1366x768_21690.jpg
http://www.edplace.com/userfiles/image/man's%20shadow.jpg
http://shop.sealomatic.net/images/1317269359817440511723.jpeg
http://www.it.iitb.ac.in/ekshiksha/images_light_VIII/figure_9.JPG
http://0.tqn.com/d/animatedtv/1/0/i/A/quimbybanner.jpg
http://shirley.moodle2.net.nz/pluginfile.php/5670/mod_imscp/content/1/ess-
sci-assets/programme-assets/images/z_block.jpg

52. http://earth.rice.edu/Space_Update/updating/spaceweather/data/sun/eclipses/eclipse_diag
ram.jpg
http://www.ambitionarts.com/images/dancer_mirror.jpg
http://cdn.instructables.com/FR4/B3NZ/GX5XJVBA/FR4B3NZGX5XJVBA.LARGE.jpg
http://media2.apnonline.com.au/img/media/images/2013/04/25/WDN_25-04-
2013_ROP_03_Periscope%20rifle%2004_fct848x522x126_t460.jpg
http://webs.mn.catholic.edu.au/physics/emery/assets/hsc_as3.gif
http://images.wisegeek.com/dentist-inspecting-a-patient.jpg
http://solarcellcentral.com/images/top_pic_csp_page.jpg
http://www.energy.siemens.com/co/pool/hq/power-generation/power-
plants/csp/solar_parabol_large.jpg
http://static.fairfaxrural.com.au/multimedia/images/large/1996913.jpg
http://olc.spsd.sk.ca/de/physics20/light/light_images/flashlight2a.jpg
http://i1063.photobucket.com/albums/t507/cmusngi2929/My%20CLS55%20AMG%20Rebui
ld/Headlights1RE.jpg
http://www.sciencelearn.org.nz/var/sciencelearn/storage/images/contexts/light-and-
sight/sci-media/images/convex-mirror/685505-1-eng-NZ/Convex-mirror.jpg
http://colorschemetools.net/cms.ashx?req=Image&imageid=7baf807d-ca1d-46dd-9eaf-
4dc50b711656&key=Additive%20color
Video Credit
http://www.youtube.com/watch?v=N1-zjbRqYXk
https://www.youtube.com/watch?v=jtTBOMVMSYM