Light

Light
- Forms of energy available on the Earth:
1- Sound Energy.
2- Heat Energy.
3- Wind Energy.
4- Electrical Energy.
5- Light Energy.
- Light: is also a form of energy.

Sources of Light:

A- Natural source of light:

1- Sun.
2- Stars.
3- Lightning.
4- Fire.
 Some animals and plants that emit light are also natural source of light.
1- Firefly.
2- Jellyfish.
3- Fungus
B- Artificial sources of light:
1- LED. 2- Bulb. 3- Fluorescent tubes.
4- Halogen lamp. 5- Computer 6- Phone.

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 Brighter and dimmer

Light Meter:

It is used to measure the amount of light either falling on a surface or

reflected from a surface.

- Some light sources are dimmer that others (such as night light is usually dimmer than a
reading light).
Because night light has less energy than reading light is being transferred from the lamp to
the surroundings.

Q- How does distance affect the brightness if a light source?

- When increasing the distance between light source and the wall the light intensity decreases.
(Brightness decreases).
- Measure brightness by using light meter.

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 Class (4)

- Investigated how distance affect the brightness of a light source.

a) They made the room dark, Why? Is this Safe?
 So, they could see the flash light shining more easily.
b) They used two flash-light, Why?
 To make comparison between two different distances.
c) They measured the distance from the flash-light to the wall, why?
 Find the relation between distance and brightness.
d) Why did they measure brightness with a light meter?
 A light meter would give an accurate reliable measurement if brightness.

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 QUIZ

1) What is the name of natural light source?

………………………………………………………………………………………………
2) What is the name of artificial light source?
………………………………………………………………………………………………
3) What is the name of a bright object that is not a light source?
………………………………………………………………………………………………
4) What is the name of three ways that humans use light?
………………………………………………………………………………………………
5) How does distance affect how bright a light source appears?
………………………………………………………………………………………………
6) Describe one way to measure brightness?
………………………………………………………………………………………………

Answers

1) Sun.
2) TV, Computer, Lamp, flashlight.
3) Moon.
4) To read by – To see where they are going – for cars.
5) The further from the light source, the dimmer the light appears.
6) By using light meter.

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 Ray diagrams:

- One characteristic of light is that it always travels in straight lines.

- Light beams: as lots of rays.
- Single light ray can be represented as straight line with an arrow.
- The arrow: show the direction in which the light ray is travelling.
- Another characteristic of the way light travels is that as beam of light moves outwards from
its source.
- It spreads out to cover a wider and wider area.

Light reflection:

- When the light falls on any object some light bounces off (OR) reflected from this object.

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 Amount of light reflection depend on that the
material the object is made from

1) Some materials do not reflect much light (these object appear dark and dull).
OR (rough materials), Ex: Wood, leather, leaf.
2) Some materials that reflect a lot of light appear bright and shiny.
OR (Smooth surface), Ex: Mirror.

Give reason:

1- The moon appears bright?

 Because it reflects a lot of light from the sun.
2- Why mirrors reflect lots of light?
 Because they are bright and shiny.

Two Types of reflection

Specular reflection Diffuser reflection
Or Regular reflection Or Irregular reflection
Ex: Mirror Ex: Wood

When the light fall on the smooth surface that When the light fall in the rough surface
reflect the light in one direction. that reflect or scattered the light in
different direction.

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 Light and Seeing

- Without light, we cannot see.

- We see a light source when the light that it emits enters our eyes.
- We see an object that is not a light source reflects from the object, entering our eyes.
- The amount of light entering our eyes affects how well we see.
- If there is not much light, we cannot see clearly.

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 Your eyes

This diagram shows the parts of the eye:

Part of the eye Description

Pupil A hole in the center of the iris where
light enters so that we can see
Eyelashes Hairs on the eyelid

Eyelid A fold of skin above the eye

Iris The colored part of the eye

Tear duct The hole though which tears flow onto

the eye
Eyebrow Hairs in the forehead above the eye

 some animals like cat its eyes glow at night because its eyes reflect the light.
 Its eyes not a light source
 To make the road safe:
Road workers put cat eyes reflectors on the road to help drivers to see at foggy
night or small light source powered by sun.

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 Light and Shadow
1. Why does the moon appear brighter at night?
…………………………………………………………………………………………………………………………………………………………

2. How is a shadow formed?

…………………………………………………………………………………………………………………………………………………………

3. What happens when light hits a mirror?

………………………………………………………………………………………………………………………………………………………..

4. Does light only travel in a straight line or can it bend?

…………………………………………………………………………………………………………………………………

5. Why is the sun so important to life on earth?

…………………………………………………………………………………………………………………………………

6. What does it mean when a material is opaque?

…………………………………………………………………………………………………………………………………

7. What does transparent mean?

…………………………………………………………………………………………………………………………………

8. List all the light sources you know.

…………………………………………………………………………………………………………………………………

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9. Make a silhouette of a friend’s head using a projector. How can you change the size
of the shadow?
…………………………………………………………………………………………………………………………………

10. What happens to a shadow when you move the object towards the light source?
…………………………………………………………………………………………………………………………………

11. Is it possible to see without light?

…………………………………………………………………………………………………………………………………

12. Can you see reflective material without light? Why?

…………………………………………………………………………………………………………………………………

13. Why is your shadow sometimes in front of you and sometimes behind you?
…………………………………………………………………………………………………………………………………

14. Draw three different light sources and label the brightest.

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 Light and Shadows Answers
1. Why does the moon appear brighter at night?
The moon appears brighter at night because light from the sun reflects off it
(bounces off it) back to the earth.

2. How is a shadow formed?

Shadows are formed by opaque objects blocking light and creating an area of
darkness.

3. What happens when light hits a mirror?

When the light rays hit the smooth mirror, they all bounce off at the same angle,
creating a clear reflection.

4. Does light only travel in a straight line or can it bend?

Light only travels in a straight line.

5. Why is the sun so important to life on earth?

The sun is so important because it is our main source of light and it gives out rays
of light and UV light. The sun helps plants to make food, it helps people to make
vitamin D and it also provides warmth.

6. What does it mean when a material is opaque?

Materials that are opaque block the light and don’t let any light rays get through.

7. What does transparent mean?

Transparent is used to describe objects that let light travel through them easily.

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8. List all the light sources you know.
Answers may include examples such as:

• the sun
• light bulb
• lamp
• lighthouse
• candle
• torch
• camera flash
• mobile phone backlight
• laser pen
• traffic light
• car light
• TV
• computer

9. Make a silhouette of a friend’s head using a projector. How can you change the
size of the shadow?
You can change the size of the shadow by getting closer to, and further away
from, the projector.

10. What happens to a shadow when you move the object towards the light source?
When you move the object towards the light source, the shadow gets bigger.

11. Is it possible to see without light?

It is not possible to see without some form of light.

12. Can you see reflective material without light? Why?

You cannot see reflective materials without light, because the reflective materials
are not light sources. The light must hit the reflective material, bounce off it and
then hit our eyes for us to be able to see it.

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13. Why is your shadow sometimes in front of you and sometimes behind you?
Shadows are formed by your body blocking the sun’s light and as the earth moves
around the sun, shadows move throughout the day.

14. Draw three different light sources and label the brightest.
Answers will vary and may include examples such as:

• the sun
• light bulb
• lamp
• lighthouse
• candle
• torch
• camera flash
• mobile phone backlight
• laser pen
• traffic light
• car light
• TV
• computer

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Electricity

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 Unit(8): Electricity
[1] Electricity: It’s the flow of an electric charge through wires to an appliance.

[2] Appliance: a piece of equipment or device designed to perform a particular job, such as:
washing machine.
[3] Battery: a device that stores electrical energy as a chemical.
Two or more cells joined together form a battery.
[4] Circuit: It is the closed path that electricity can flow around.

Simple Circuit:

To make a simple circuit you need the following circuit components:

1- Lamp.
2- Lamp holder.
3- Wires.
4- Cells (Battery).
5- Cell holder.

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 Science of context:

- The American inventor, Thomas Edison, designed light bulbs that are still used by many of us today!
However, these light bulbs only transfer a small amount of the energy (electricity) they have, as
light.

- Electricity can also damage the environment, It is often generated by burning coal, we can help to
protect the environment by using:
1) Solar panels.
2) Wind turbines.

1) Solar panels:
 They use the power of the sun to generate
electricity.

2) Wind turbines:
 They use the power of the wind to produce
electricity.

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 Use Different Components:
- There are other components we can put into a circuit that will also transfer energy. For example:
(1) A Buzzer: Makes a noise in a complete circuit.
(Or used to make a sound).

(2) A Motor: Produces movement in a complete circuit.

(Or used to make something spin around).

Compare between complete circuit

and incomplete circuit

complete circuit incomplete circuit

Electricity can flow, There is a break in the circuit that
and the components will work presents the electricity from flowing.
and the components will NOT work

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 Look for switches:

- Switches can be used to open or close a circuit.

- When off, a switch “breaks” the circuit to stop the flow of electricity.

- When in, a switch “completes” the circuit and allows the electricity to flow.

- Types of switches:
(1) Push-button switch.
(2) Slide Switch.
(3) Toggle switch.

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Classify the materials according to conduct electricity into Two types:
1- Electric Conductor: is a material that will allow electricity to flow through it. Such as:
• Copper Wire.
• Paper Clip.
• Metallic Coins.
• Metallic Key.
• Iron Nail.

2- Electric Insulator: Materials that do not allow electricity to flow through. Such as:
• Wood.
• Plastic.

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- Appliances: Many everyday appliances rely on electricity for them to work.
Some appliances use Mains electricity.

o Mains electricity: are plugged into a socket. o Others have a battery to

make them work.
o Examples:
 Appliances that use mains electricity:

• Tasters.
• Television.
• and washing machine.
 Appliances that use battery:

• Mobile phones.
• and Torch.

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 More Than one Lamp?

- A cell has positive and negative terminals.

- The cell has voltage.
- Voltage: is the size of the push that comes from the cell.
- The Push: is what makes electricity flow around the circuit.
- The bigger the number of volts the more push the cell gives.

- Series Circuit: It is the circuit in which each component follows one after the other in one road
(Single Pathway).

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 Compare between Series Connection
and parallel Connection
Series Connection Parallel Connection
It is a way in which the light bulbs are It is a way in which the light bulbs are
connected one after another in one route. connected in branching routes.

The light intensity of one bulb is strong.

The light intensity of one bulb is strong.
The light intensity of more one bulb
become weak. The light intensity of more one bulb is
similar.
Light intensity decreases.
Light intensity doesn’t change.

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23
Volcanoes &
Earthquakes

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 Unit(9): Volcanoes and Earthquakes
The Earth:
o Most of the earth is covered in water nearly three quarters of it is made up of seas and
oceans.
o And one quarter is made of land.
o The earth is made of rocks.

Rocks:
o Rocks are naturally existing solid matter that exist in nature and are made up of
combinations of one or more minerals.
- Three types of Rocks:
[1] Igneous rocks.
[2] Sedimentary rocks.
[3] Metamorphic rocks.

[1] Igneous rocks: divided into:

A- Intrusive igneous rocks.
B- Extrusive igneous rocks.

A- Intrusive igneous rocks:

 These rocks formed inside the Earth’s surface from magma.
 Examples:
1- Gabbro rock.
2- Diorite.
3- Granite.

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 B- Extrusive igneous rocks:
 When the molten matter of magma come out of the Earth’s surface by rupturing
it, it’s known as lava.
 This lava too, cools down and form extrusive igneous rocks.
 Examples:
1- Basalt.
2- Obsidian.
[2] Sedimentary rocks.
o Sedimentary rocks are made of sediments like particles of sand, shell and pebb.
o How are they formed?
 By three steps:
1- Weathering.
2- Erosion.
3- Sedimentation.
4- Examples:
1- Sand-stone.
2- Lime-stone.
[3] Metamorphic rocks.
o Due to extreme temperature and pressure the (igneous and sedimentary) undergo
physical and chemical changes called metamorphosis.
 Examples:
1- Gneiss and Marble.

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- What is the earth like inside?

There are 4 main layers:

[1] Crust: This is the thinnest layer of the earth, it is only about 20 km thick,
some parts are thicker than others, the thinnest parts are under the oceans.

[2] Mantle: this layer is made of solid and liquid rocks. And it locates
underneath the crust.
[3] Outer-core: this is the layer beneath the mantle and is made of liquid iron
and nickel (Two metals).
[4] Inner-core: this layer is made of solid iron and nickel (Two metals).

 The Earth’s crust: is the layer on which we live.

 It is made of mountains, plateaus, sea-beds, and valleys.
 The Earth’s crust has thickness 50 km thick. It is thinner under oceans, and
thicker under the mountains.

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Volcanoes:

o When a volcano erupts, it sent up molten rock called lava.

o Lava comes from underneath the Earth’s crust (in the mantle).
o What is the name of material in the mantle?  Magma
o Magma:
 Hot liquid rock formed just below the surface of the Earth.
o But Lava:
 Molten rocks that erupt from a volcano.
o What is the main features of a volcano?
[1] Magma: molten rocks deep below the Earth’s surface.
[2] Main Vent: an opening in the Earth’s crust through which magma is forced
upwards in the center of volcano.
[3] Lava flow: molten rocks running down the volcano sides.
[4] Crater: The open, almost circular top of the volcano.
[5] Secondary vent: a sideways vent from the main vent.
[6] Layers of ash and lava: made from other eruptions of the volcano as the lava
cools and flows down the sides of the volcano.
[7] Ash cloud: small piece of rock thrown cut in of the top of the volcano crater.
[8] Conduit: an underground passage which magma travels through

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 o Where do we find volcanoes?
 They are near the edge of plates.

o Volcanologists: are scientists who study volcanoes.

- The Three Stages of Volcanoes

o Active: An active volcano is one that has erupted recently, and there is the
possibility that it may erupt again.
o Dormant: Not active, but can be active again.
o Extinct: An extinct volcano is one which has erupted thousands of years ago,
but it will probably never erupt again.

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Natural Disasters:

o Earthquake: a natural disaster that happens when tectonic plates suddenly

start moving.
o Seismologists: are scientists study the movement of the Earth’s plates.
o Seismograph: this is the chart of the earthquake.
o Foreshocks: before and
earthquake happens there are
smaller earthquakes, these
are called foreshocks.

o The bigger the lines on the

seismograph the bigger the
earthquake.

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Earth In
Space

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 Unit(9): Earth In Space
The Solar System Consist of:
(1) Sun.
(2) Eight Planets.
(3) Moons.
(4) Asteroid.
(5) Comets.

- Solar system formed about 4.6 billion years ago.

- It came from a huge circle of gas and dust left behind when the sun formed.
- Sun and near the sun the rocky inner planets (Mercury, Venus, Earth and Mars).
- Then come the outer planets called the gas giants (Jupiter, Saturn, Uranus and
Neptune).

- Pluto is a planet or not?

- Scientists say that far can object to be classified as a planet it must:
[1] Orbit the sun.
[2] Be big enough to have formed a sphere.
[3] Be big enough to have cleared the path of its orbit to other objects.
- Pluto is not planet because it did not meet one of the above points.

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[1] The Sun:
- A star.
- A huge, glowing ball of fire.
- Source of heat and light.
- It is the center of the solar system.

[2] Planets:
- Objects rotates around the sun in fixed orbits.
- (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune).
[1] Mercury:
 Smallest and closest planet to the sun.

[2] Venus:
 Hottest and brightest planet.
 Size is similar to the Earth.
 Also called sister planet of Earth.

[3] Earth:
 Only planet on which life exists.
 Also called “Blue Planet" because almost 70% of
its surface covered with water.

[4] Mars:
 Also called “Red Planet” because the soil and
rocks on this planet are red in color.
 Scientists believe that besides Earth, Mars can
also support life.

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 [5] Jupiter:
 Largest planet in the solar system.
 Heavier than all the planets taken together.
 Fastest spinning planet.

[6] Saturn:
 Known for the bright rings around it.
 Easily seen in the night with the help
of telescope.

[7] Uranus:
 Very cold and consists of cold gases.
 Seen only through a very powerful telescope.

[8] Neptune:
 Both Uranus and Neptune are called outer
planets.
 Also has rings like Saturn.

[3] Moon and Satellite:

- An object that revolves around a planet is called
Satellite.
- Almost all planets have Satellites.
- The Moon revolves around the Earth.
- It is the only natural Satellite of Earth.
- The moon does not have light of its own.
- It reflects back the light of the sun falling on it.

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► What is in space?

- Asteroids: these are pieces of rock and ice. Most of them are in an area
orbiting the sun called the asteroid belt.
- Asteroid Belt: this are between Mars and Jupiter. Asteroids revolve
around the sun inside it.
- Comets: are big lumps (masses) of ice and it consists of head and tail.
- Halley’s Comets: is a famous comet that is seen in our sky every 76 years.
- When will we see in again?
 2062 for example

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► The Earth Moves:

 Revolution and rotation of the Earth:

[1] When the Earth revolve around the sun in fixed orbit called revolution causes 4
Seasons.
, The Earth makes one complete revolution around the sun once every 365.25 days.
[2] When the Earth rotates around its axis called rotation causes day and night.
, The Earth makes one complete rotation around its axis once every 24 hours.
- The Earth’s Axis:
 Is an imaginary line that goes from the North pole at the top to the south
pole at the bottom.
- The Earth spins or rotates all the time.
- The Earth is spinning anti-clockwise.

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► The Sun’s apparent movement:

- The Earth takes one day (24 hours) to make one complete rotation; due to the
Earth’s rotation.

- The Sun appears to move across the sky over the course of the day.

- It appears over the eastern horizon at down rise in the sky reaching its
maximum height at about noon (midday).

- During afternoon, the Sun “Sinks” in the sky, disappearing over the western
horizon at sunset.

- We now know the Sun does not move. It only appears to be moving because
the earth is spinning.

- Observe the sun:

- We should not look directly at the sun
- Galileo did this and he eventually went blind.
- It is not safe.
- We can observe the Sun by looking at the shadows it casts.

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