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المدير العام علم بلدك :

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unitit 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
[center]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 [/center]

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