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.
Citation preview
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 theres no light?
3. Where does light come from?
4. Sun is our major light source!
5. If theres 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 arent
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
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!
14. Phases of the moon.
15. Mid-autumn festival is celebrated on the 15th of the 8th
month in the Chinese calendar (full moon).
16. Hari Raya Idulfitri is celebrated at the end of Ramadan,
marked by the appearance of new moon on the last evening of
Ramadan.
17. 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.
18. 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.
19. Reflection of Light
20. 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).
21. The texture of the surface affects the type of reflection
that occurs at the surface. regular reflection (Specular) irregular
reflection (Difuse)
22. Have ever cut your hair in barbershop?
23. Plane mirror b a The images formed by a plane mirror are
upright, same size (undistorted), virtual and laterally
inverted.
24. Plane mirror dance studio room looks larger
25. Periscope Periscope is used to change the direction of
light by reflection.
26. Concave mirror The shape bends inwards. The images formed
by concave mirror are virtual and magnified if the object is put
near the mirror.
27. The uses of concave mirror
28. Concave Mirror used in Reflecting Telescope
http://www.bro.lsu.edu/telescope/Classroom/2.How%20Telescopes%20Work/Reflecting.gif
29. Concentrate Solar Power on Youtube
30. 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.
31. The uses of convex mirror
32. 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
33. 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. 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.
39. 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.
40. 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.
41. 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.
42. Colours
43. 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!)
44. 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.
45. 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
