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المدير العام علم بلدك :

Unit 1 : Energy
Lesson 1 : light

Light :الضوء
A form of energy that Can be seen by the
eye .

الضوء هو صورة من صور الطاقة التي
تؤثر على العين مسببة الإحساس بالرؤية .

Difference between light energy and other forms of energy :

الاختلاف بين طاقة الضوء والطاقات الأخرى

Lightenergy differ
than other kinds of energyتختلف طاقة الضوء عن
الطاقات الأخرى
Because :
It is visible energy .
لأنها طاقة مرئية
Sources
of light : الضوء
مصادر
1. The
Sun :
The main source المصدر
الرئيسي of light on earth's surface
2. The
moon :
Moon reflects sunlight that falls on its
surface .
3.Torch
– electric lamp – candles –kerosene lamp
Visible
Spectrum الطيف المرئي
:
The Light energy which can be seen by
the eye .

Travel of light

v Light travels in straight lines.
Activity prove that :
Light
travels in straight lines
Tools : lighted candle – straight cylinder of length 50 cm
Steps :
1.Fix a lighted candle vertically .نثبت
شمعة مشتعلة راسيا
2.Put one of the 2 ends of the straight
cylinder .
in front of the candle flame ضع
احد طرفي الاسطوانة المستقيمة أمام لهب الشمعة
3.Look at the flame of the candle .
Observation :
You can see the flame يمكن رؤية
لهب الشمعة
4.Bend the cylinder (not straight ) أثنى
الاسطوانة
5.Try to look at the candle flame
through the bent cylinder
Observation : طرفي الاسطوانة المنثنيةانظر إلى لهب الشمعة من احد
You can't see the flame. لا
يمكن رؤية لهب الشمعة
Conclusion :
Light travels in straight lines . ينتقل
الضوء فى خطوط مستقيمة

Activity prove that :
Light
travels in straight lines
Tools : lighted candle – 3 cardboard screens
Steps :

1.Bring 3 pieces of
cardboard , each containing a hole .نحضر 3 قطع ورقكرتونبها
ثقب ضيق نحضر 3 قطع ورقكرتونبها

2.Put them in a row in
front of a lighted candle . نضعهم فى صف واحد مع لهب الشمعة
Where all holes and the flame are on one
straight line .
3.Look to the candle flame through the
hole of the last pieces of cardboard .
انظر إلى لهب الشمعة من فتحة القطعة الأخيرة
Observation :
You can see the flame يمكن
رؤية لهب الشمعة
4.Move any of the pieces of the
cardboard to right or left نحرك احدهما
The 3 pieces are not on one straight line .
5.Try to see the candle flame through
the
hole of the last pieces of cardboard .
Observation :
You can't see the flame .
لا يمكن رؤية لهب الشمعة
Conclusion :
Light travels in straight lines

Phenomena
ظواهر تحدثhappen due to Travel the light in straight lines :

1.Formation of inverted
images through narrow holes . تكون صور مقلوبة خلال الثقوبالضيقة
2.Formation of shadows .تكون الظل

Formation of images through narrow holes :
When
light travels through narrow holes :
An inverted image is formed is formed .
عندما ينتقل الضوء خلال الثقوب الضيقة
تتكون صورة مقلوبة
It leads to : هذا أدى إلى
Designing of photographic camera . تصميم
كاميرا التصوير
Properties of image formed through narrow
holes
1. Inverted (upside down )
2. Minimized
Activity proves that :
Light
travels through narrow holes forming An inverted image :
Steps :
1.Bring a cardboard ( metallic ) box
opened from on side .

نحضر صندوقكرتون
مفتوح من احد جوانبة

2.Cover the open side by a semi-transparent paper
(white balloon )

نغطى الجانب المفتوح بورقة نصف شفافة كبالونة
بيضاء

3.Make a small hole on the opposite side of the box . نصنع ثقب فى الجانب المقابل
In a dark room :
4.Move a lighted candle in front of the
small hole . نحرك الشمعة امام الثقب
of the cardboard box Until an inverted
is formed . حتى تتكون صورة مقلوبة

Observation :
An inverted and minimized image for the
candle is formed
.تتكون صورة مقلوبة للشمعة

Conclusion :
Light
travels through narrow holes in straight lines forming An inverted (upside down ) image.

v
This activity
is the base of idea of the camera
v
This box is called
pin-hole camera

Al.Hassan Ibn El.Haitham

Invent pin hole camera

Explain vision

Primary 5
Mr. Mohab Elsakka
Teacher
Of Science & Physics & Chemistry
0122897271
Email :
mohabphysics_mohabphysics* yahoo.com
Task 1

Q1 : Complete ?
1.Image formed in pin-hole box is ……………and
…………. .
2.Moon reflects ……….……light
falling on its surface .
3.Light travels in …………….……….lines
.
4.From sources of light …………………….and
……………………….

Q2 : Write the Scientific term ?
1.A form of energy that can be seen by
the eye (……………………….)
2.The main source of energy on earth's
surface (……………………….)
3.Light energy which can be seen by the
eye (……………………….)

Q3 : Give Reasons ?
1.Formation of inverted image through
narrow holes .
………………………………………………………………………………
2.Moon is considered as a source of
light
………………………………………………………………………………

Definition of Shadow
:
A dark area formed by an opaque body
that block the light .
N.B :
The nearer object
to the light source has the biggershadow .
An activity to show formation of shadow :
Steps :
1.Put your hand between the candle
(lighted source) and the wall
2.Observe what happens
Observation :
A dark area is formed on the wall.
Conclusion :
1. Shadow (umbra) is :
The dark area which is formed behind the
body when light falls on it .
2.Area and position of shadow changes:
By changing the position of the object
from (relative to) light source
Reason of shadow :
Shadow is formed
:
Due to travel of light in straight
lines.
An activity to show formation of shadow :
Steps :
Put the book between the light source
and the wall .
Observation:
Shadow is formed for the book on
the wall.
Conclusion :
Shadow is formed Because light travels
in straight lines
Al.Hassan Ibn El.Haitham :
The first Arabic scientist
who explain the vision of objects (bodies
)
Because :
light falls on the bodies and reflects
to eye causing vision .
The idea of Making of
photographic camera :
The activity of the candle and the dark
box .
The travel of light in straight lines
Laser light :
Is a light ray that travels for long
distances Without fainting .
Uses of Laser light : Communication –Medicine –
Computers

Opaque & Translucent and Transparent objects
Transparent
material

Translucent
material
Opaque
material

The material that
Allows most light to pass
through it .

The material that allows ( lets )
Some light to pass
Through it .
The material that doesn't allow light to pass through it

objects can be seen through clearly
(with details )
objects can be seen through it less clearly .
objects can't be seen behind it (
through it ) .
Glass (as cup )
Air
Water
Clear glass of window
Tissue paper
Frosted light bulbs
Cardboard (cartoon )
People
Wood
Books
Rocks
foil paper

· Transparent
Material :Most light passes
through
· Translucent
Material:Some light passes through
· Opaque
Material : No light passes through
Activity to show the Types of objects:
Tools :
Photographic picture
– clean transparent glass plate
Tissue paper ( handkerchief ) -
cardboard paper .
Steps :
1.Put a glass plate over the
Photographic picture
2.Try to see the picture behind the
glass plate clearly .
Obs. :
You can see the picture clearly
Conc. :
Glass is a Transparent material .
3.Put handkerchief on the picture
Obs. :
You see the picture with less clearness
Conc. :
handkerchief is a Translucent material .
4.Put cardboard paper over the
Photographic picture
Try to see the picture behind the
cardboard paper clearly .
Obs. :
You can't see the picture .
Conc. :
The cardboard paper is an opaque
material .
Conclusion :
Materials are divided into 3 types : Opaque & Translucent and Transparent objects .

Task 2

Write the Scientific term ?
1. A dark area formed by an
opaque body that block the light .
2. The first Arabic scientist
who explain the vision of objects (bodies ).
3. Is a light ray that
travels for long distances Without a reduction of its intensity .
4. The substance where
things can be seen through it clearly .
5. The substance through
them things can be seen but with less clearness
6. The substance that doesn't
pass light through it and things can't be seen from its back .
Complete ?
1..……………………is a transparent Material ,
While ……………………..is a translucent Material , and …………………..is an Opaque
Material
2……………..is formed when an ……………..body
blocks the light .
Give Reasons ?
1.Formation of shadow.
2.Glass is a transparent material
3.Cardboard paper is n opaque material

Definition of Light
Reflection :
Bouncing (Rebounding) (returning back )
of light when it fall on Plane ( shiny ) objects .
Reason of vision ?
We see things around us :
When things reflect light falling on
them to reach the eye
% You don't see the objects in the dark room .
% You can see the objects inside the room when you switch on
the electric bulb .
Types of Light
Reflection :
1.Regular Reflection
2.Irregular Reflection

Regular Reflection
Irregular
Reflection

Falling of a light on the surface of
a plane (smooth) mirror
with a certain angle
(in a certain direction)
Falling of a light on the surface of
a rough shiny plane
(not smooth) mirror as white paper
Light reflects ( rebounds ) to the back
with the same angle .
Light reflects ( rebounds ) and spreads
to different directions .
To reach the eye To see the image
object.

The eye can't see the image .

plane shiny surface

Rough shiny surface

Applications on light
reflection :
% When you stand in front of a plane mirror :
You can See your image at equal
distance to the distance between you and the mirror .
Example :
· If the distance between you and the mirror equals 20 cm :
· The distance between your image and the mirror = 20 cm
· The distance between you and your image = 40 cm.

:

Light refraction:
Change in the direction of light rays
when it travels between 2 transparent media as water and air due to
change in light speed .
Light refracts :
When it travels inclined (
by angle ) from a transparent medium as water to another transparent medium as air .
Due to change in light speed where :
Light speed in water is less than that
in air
An activity to show light refraction :
Steps :
1.Look at the bottom of a cup filled
with water
Obs. :
The bottom of the cup appears in a
higher position than its real position 2.put a spoon inclined inside
the cup :
3.Look at the immersed part of the
spoon
Obs . :
The immersed part appears broken (bent )
Conc . :
Light refracts when it travels between 2
transparent media as water and air
Phenomena happen due to light
Refraction:
1.Appearance of the spoon bent (broken)
in a cup of water .
2.Appearance of the pencil bent
(broken) in a cup of water .
3.Appearance of the cup bottom higher
than its real position
4.Appearance of the fish higher than
its real position .
5. Appearance of the bottom of the basin
higher than its real position .

Spectrum Colours ( Rain bow )
:
A group of 7 colours that appear in the
sky after rainfall .
White light :
A group of 7 colours that form the
white light .
Which are :
1. Red 2.
Orange 3. Yellow
4. Green 5.
Blue 6. Indigo
7. Violet
% The first colour of Rain bow : Red

% The last colour of Rain bow : Viloet
% The middle colour of Rain bow :green

Reason of appearance of spectrum colours :
Due to Light separation (splitting )
analysis (dispersion )

Ways of obtaining spectrum colors :

1.by water
droplets :
% Water droplets suspended in the air (act as prism )
analyze sunrays
That falls on them into 7 Spectrum Colours .
2.By a glass prism :
· when white light falls inclined on a glass prism :
· it separates into 7 spectrum colors

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