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.
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
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.
A thin line of light coming from a source is
called a light ray.
A bundle of light rays is called a beam of
light. A beam of light can be parallel,
divergent or convergent.
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
• If the object is translucent, some light can pass through,
but the rest of the light will be reflected.
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
How does sunlight cause
the Sun appears
to rise in the
...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
Mid-autumn festival is celebrated on the 15th of the 8th month in
the Chinese calendar (full moon).
Hari Raya Idulfitri is celebrated at the end of Ramadan, marked by the
appearance of new moon on the last evening of Ramadan.
The moon blocks the light
from the sun
An observer on the earth
will experience total
The shadow of the moon is
formed on the earth.
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.
How the light is reflected?
i= angle of incidence
r = angle of reflection
The incident ray, reflected ray and the
normal at the point of incidence all lie in the
The „angle of reflection‟ is always equal to
the „angel of incidence‟ (i = r).
The texture of the surface affects the type of
reflection that occurs at the surface.
The word “AMBULANCE” is written laterally
inverted at the front of an ambulance.
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
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
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.
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
1. The dispersion of
white light is the
splitting up of white
light into its
2. The different colours in white light
are refracted through different angles
by a glass prism. This results in the
dispersion of white light.
White light is made up of seven different
colours (Red, Orange, Yellow, Green, Blue,
We classify these colours as
primary and secondary
Primary colours are basic colours that can not be obtained by
mixing other colours together. Primary colours are: red, green,
Secondary colours are formed by mixing primary clours.
Secondary colours are: cyan, yellow, magenta.
How do we see colour?
Light from most light
sources looks white, but
actually contains all the
colours of the spectrum;
also known as the
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!)
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.
Joan Fong. Lower Secondary Science Matters Volume B Second Edition. Marshall Cavendish.