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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

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

[مستر عبدالرحمن المغربى]

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