1.
Light
Seán Finn
Department of Education
UCC

2.
Light sources.
All of these objects can be seen in the dark
because they let out their own light-they are
luminous

3.
How do we see objects that do not let out their
own light i.e. non luminous bodies?
• We can see them
when light from
another source
reflects from them.
• We will not be able
to see these objects
in the dark.
Killarney by night

4.
Light travels from a source
When it is ABSOLUTELY
DARK you cannot see
anything at all
There might be
something HERE …
…but you cannot see it

5.
Light travels from a source
…bounces off it and
travels to your EYE
EYE…
But in the daylight
RAYS OF LIGHT
RAYS OF LIGHT from
the SUN
SUN travel to this
object…
…and NOW
NOW you can see it

6.
Light travels from a source
There are actually many RAYS OF
RAYS OF
LIGHT
LIGHT bouncing off the object but
the diagrams become too
complicated if you put them all in

7.
Do all substances allow light to
pass through them?
Light will not pass through
substances like aluminium
foil.
Light will pass easily
through substances like
glass
Some light will pass
through certain substances

8.
Opaque materials do not allow
light to pass through them.

9.
Transparent materials
Light will pass very
easily through some
materials
cling film
glass window
plastic bottle
They are said to be
TRANSPARENT

10.
Translucent materials
You cannot SEE through
a sheet of greaseproof
paper like you can see
through glass
But if you shine a torch
behind the greaseproof
paper you can see the
light but NOT exactly what
the torch looks like

11.
D esign and makea model glasshouseusing a plastic
bottlethatwill allow lightto pass through
A cloche
Place thermometer in bottle next to light.
Note that the temperature of the air in the
bottle increases.

12.
Investigation: Light travels in straight lines.
A
B
C

13.
How light travels
…you can see
the view out of
the other end
If you look
through a long
cardboard
tube…

14.
How light travels
…you cannot
see anything
out of the other
end
If you bend the
cardboard tube
and then look
through it…

15.
How light travels
This is because light
travels in
STRAIGHT LINES
In this tube there is a
straight line from
one end to the other
In this tube there is
only a straight line
UP TO HERE
The light CANNOT go
any further

16.
How shadows are formed
There many of rays of
light travelling in
STRAIGHT LINES
STRAIGHT LINES from
the torch
Some travel PAST
PAST the
ornament….
…but others “BUMP
BUMP
INTO
INTO” the ornament and
cannot travel any
further

17.
Formation of shadows
torch
the OBJECT
OBJECT is
blocking the
light here
Light from the torch travelling in a
straight line CANNOT
CANNOT get behind
the OBJECT
OBJECT
OBJECT
OBJECT SHADOW
SHADOW on wall

18.
Size of shadows
If light was able to travel in CURVES
CURVES
then we would not get SHADOWS
SHADOWS
BUT LIGHT
ONLY
TRAVELS IN
STRAIGHT
LINES

19.
Size of shadows
As the toy is moved towards the
wall the shadow gets smaller
shadow getting smaller

20.
Size of shadows
shadow getting smaller

21.
Size of shadows
shadow getting smaller

22.
Size of shadows
shadow getting smaller

23.
Size of shadows
LARGE SHADOW
when the toy is
close to the light
SMALLER
SHADOW when the
toy is further from
the light
TINY SHADOW
when the toy is a
long way from the
light

24.
Formation of shadows

25.
By using a mixture of
opaque, translucent and
transparent materials
you can create shapes
to produce shadow
puppets
Shadow puppets
Here a simple cardboard shape (opaque)
has holes made in it (transparent) to
provide eyes and a mouth

26.
This is a picture of a very
complicated shadow
puppet
It is made from opaque wire
and transparent materials that
are also coloured giving the
shadow produced a very
colourful appearance
Shadow puppets

27.
Shadows from the sun
Here you can see shadows
formed outside by the SUN
Notice that the shadows are
different sizes at different
times of the day
SHORT, VERY
DARK shadow
LONG, LIGHTER
shadow

28.
Shadows from the sun
To see how shadows
change during the
day stand in a FIXED
position and then get
someone to draw
round your shadow
using chalk or water-
based paint
A few hours later
stand in EXACTLY the
same place and
again get some one
to draw around your
shadow

29.
Shadows from the sun
This will show you how much
shadows change over a few hours
To see how shadows
change during the
day stand in a FIXED
position and then get
someone to draw
round your shadow
using chalk or water-
based paint
A few hours later
stand in EXACTLY the
same place and
again get some one
to draw around your
shadow

30.
Measuring shadows

31.
Measuring the length of shadows
On a SUNNY day set up a
stick on a clear piece of
ground
Using a ruler CAREFULLY
measure the length of the
shadow
Notice what time it is and
then record your result in a
table like this

32.
Table of results
4.00 pm
3.00 pm
2.00 pm
1.00 pm
12.00 noon
11.00 am
10.00 am
47 cm
9.00 am
Length of
shadow
Time
EVERY HOUR go
back to the stick and
again measure the
length of the shadow

33.
Size of shadows
10.00 am 12.00 noon
2.00 pm 4.00 pm

34.
Table of results
49 cm
4.00 pm
45 cm
3.00 pm
42 cm
2.00 pm
35 cm
1.00 pm
22 cm
12.00 noon
37 cm
11.00 am
43 cm
10.00 am
47 cm
9.00 am
Length of
shadow
Time
These results can
then be put into a
BAR CHART to help
you see a PATTERN
in your results

35.
Shadows during the day
0
5
10
15
20
25
30
35
40
45
50
Length
of
shadow
(cms)
9 am 10 am 11 am 12 noon 1 pm 2 pm 3 pm 4 pm
Time
The bar chart shows that the
shadow is shortest at 12 noon

36.
Light and dark
The light is broken up
into dark and light
stripes
This is a ray
of light
shining from
a torch
Put a
comb in
front of
the torch
The comb lets light
through the gaps, but
stops it passing through
the prongs

37.
Day and night

38.
The Earth moves, the Sun stays still
This is the Sun
This is the EARTH
looking down on
the Arctic
These are the rays
from the SUN
lighting up the
EARTH
This is the half of the
Earth that light from
the Sun reaches - DAY
This is the half that
light from the Sun does
NOT reach - NIGHT

39.
The sun gives us heat and light
without which we could not live

40.
Light is a form of energy

41.
Experiment: To make a solar
panel
Perspex sheet
Water
Thermometer

42.
Light is made up of seven colors.
-The spectrum

43.
Making a spectrum

44.
The rainbow.

45.
Making a spectrum

46.
Making a spectrum

47.
Mixing of light

48.
Not all objects reflect light.
• Black objects
absorb all light
and do not
reflect any.
• White objects
reflect all light
• Red objects
absorb blue and
green light and
reflect red light.

49.
Reflection
• We see most objects
because they reflect light.
• Most objects reflect light is
a diffuse way.
• In some objects that are
smooth and opaque regular
reflection occurs.

50.
Activity: To investigate
reflection
• Place mirror on white paper.
• Shine a ray into the mirror at an angle.
• Note the position of the reflected ray.
• Change the angle at that the ray makes by
moving the light box.
Ray box
Mirror

51.
The periscope
Two mirrors
parallel to each
other at 450

52.
Making a periscope

53.
Curved mirrors

54.
Concave mirror
Concave mirors can produce images
that are right way up or upside down
also larger or smaller. If you place your
face close to the mirror your image will
by magnified and right way up.
Use: Shaving and make-up mirrors

55.
Convex mirrors
• Always produce an image that is right way
up and diminished.
• They are used seeing around corners and in
shops for security.

56.
Refraction

57.
To investigate refraction
• Shine a ray of light through a glass block at
an angle.
• Look at the ray of light in the glass from
above.
• Increase the angle between the glass and the
ray box.
• What do you notice?

58.
Why does refraction occur?

59.
Refraction

60.
To investigate refration in a
liquid

61.
Lenses

62.
Explore how objects may be magnified using
simple lens or magnifier

63.
Lenses opperate due to refraction

64.
Use of lenses
• Camera
• Telescope
• Binoculars
• Glasses
• Microscopes

65.
The telescope
• Two convex lenses, the
objective and the eyepiece.
• Eyepiece has a short focal
length
• Objective has a long focal
length
• Object to be observed at
least 10 m away.
• Telescope has to be
focused by varying
distance between lenses
(sum of focal lengths)
• Magnification is the ratio
of focal lengths

66.
Be aware of the dangers of excessive
sunlight dangers of looking directly at the
sun effect of the sun’s rays on skin
•Sunlight contains ultra-violet
(UV)light.
•If sunlight enters the eye it
will kill the cells of the retina.
These will not grow back.
•. UV light on the skin causes
sunburn and aging of the skin
and may caues skin cancer.
•Suncream absorbs UV light

67.
The telescope

68.
D esign and make model telescopes
Tubing
Plastic wrap

69.
Appreciate the importance of sight
The iris
controlls the
amount of
light entering
the eye
Bright Dark

70.
Structure of the eye
The lense of
the eye
focuses light
onto the retina
which is
carried to the
brain via the
optic nerve

71.
Understand the role of sunlight in
photosynthesis
• Plants make their own food using sunlight in a
process called photosnthesis.
• Without light plants cannot grow.
• We eat plants for food or we eat animals/ animal
products that have eaten plants.

72.
Why the Moon seems to change
The MOON looks different
depending on where it is in
relation to the SUN
From the Earth you cannot
see any light hitting the
Moon in this position
New Moon
This is what the
Moon looks like
from Earth

73.
Waxing crescent
This is what the
Moon looks like
from Earth
Why the Moon seems to change

74.
Last quarter
This is what the
Moon looks like
from Earth
Why the Moon seems to change

75.
Waxing gibbous
This is what the
Moon looks like
from Earth
Why the Moon seems to change

76.
Full Moon
This is what the
Moon looks like
from Earth
Why the Moon seems to change

77.
Waning gibbous
This is what the
Moon looks like
from Earth
Why the Moon seems to change

78.
Waning crescent
This is what the
Moon looks like
from Earth
Why the Moon seems to change

79.
To demonstrate why the shape of
the Moon changes

80.
Solar Eclipse

81.
Lunar Eclipse

82.
It is VERY
DANGEROUS to look
DIRECTLY at the Sun
or at a REFLECTION of
the Sun – it could
make you BLIND

83.
Infants and Junior Classes
(Teacher guidelines)
• Identify different light sources
• Explore the effect of light on materials
• Identify materials that are transparent or
opaque.
• Experiment with shadows and reflections

84.
Middle and senior classes
(Teacher guidelines)
• Distinguish between natural and artificial sources
of light.
• Explore that white light is made up of many
different colours.
• Investigate how light rays change direction as they
pass through water and learn that this process is
called refraction.
• Understand that mirrors and other shiney surfaces
can change the direction of light.
• Explore how lenses are used to make things look
bigger and smaller.

85.
Science Curriculum.
Infant and Junior Classes

86.
Science Curriculum.
First and second classes

87.
Science Curriculum.
Third and fourth classes

88.
Science Curriculum.
Fifth and sixth classes