LightLight

44thth Grade Science Grade Science

Core ContentCore Content

Unifying ConceptsUnifying ConceptsSC-04-4.6.2SC-04-4.6.2• Students will: Students will: • analyze data/evidence of the Sun providing light and analyze data/evidence of the Sun providing light and

heat to earth;heat to earth;• use data/evidence to substantiate the conclusion use data/evidence to substantiate the conclusion

that the Sun’s light and heat are necessary to that the Sun’s light and heat are necessary to sustaining life on Earth.sustaining life on Earth.

• Simple observations, experiments and data Simple observations, experiments and data collection begin to reveal that the Sun provides the collection begin to reveal that the Sun provides the light and heat necessary to maintain the light and heat necessary to maintain the temperature of Earth. Evidence collected and temperature of Earth. Evidence collected and analyzed should be used to substantiate the analyzed should be used to substantiate the conclusion that the sun’s light and heat are conclusion that the sun’s light and heat are necessary to sustain life on Earth.necessary to sustain life on Earth.

Essential QuestionsEssential Questions

• How does light How does light travel?travel?

• What happens What happens when light strikes when light strikes an object?an object?

VocabularyVocabulary

• ReflectionReflection – The bouncing of light off an object. – The bouncing of light off an object.• RefractionRefraction – The bending of the path of light when – The bending of the path of light when

it moves from one kind of matter to another.it moves from one kind of matter to another.• AbsorptionAbsorption –The stopping of light when it hits a –The stopping of light when it hits a

wall or other opaque object.wall or other opaque object.• OpaqueOpaque – Reflecting or absorbing all light; no – Reflecting or absorbing all light; no

image can be seen.image can be seen.• TranslucentTranslucent – Allowing some light to pass – Allowing some light to pass

through; blurry image can be seen.through; blurry image can be seen.• TransparentTransparent – Allows most light to pass through; – Allows most light to pass through;

clear image can be seen.clear image can be seen.

Light EnergyLight Energy

• Did you know that energy is the Did you know that energy is the ability to cause things to change. ability to cause things to change. – Ex. The energy in a fire changes a sheet Ex. The energy in a fire changes a sheet

of paper into ashes. of paper into ashes. – The heat from a fire can change your The heat from a fire can change your

hands from cold to warm.hands from cold to warm.

• Light is also a kind of energy. Light is also a kind of energy.

Light Energy cont’d.Light Energy cont’d.• Without light energy, you Without light energy, you

could not see anything.could not see anything.– Light gives things colors. Light gives things colors.

• Light energy can make Light energy can make many changes.many changes.– The sun shines on the soil, The sun shines on the soil,

and plants growand plants grow– Doctors use light energy to Doctors use light energy to

perform operationsperform operations– Light energy can make Light energy can make

cars move. cars move. – In space, satellites and the In space, satellites and the

space station use solar space station use solar cells to change light cells to change light energy into electricity.energy into electricity.

ShadowsShadows• Shadows occur Shadows occur

when an object when an object blocks light. blocks light. – When you put your When you put your

hand in front of a hand in front of a lamp, you make a lamp, you make a shadow on the wall shadow on the wall because your hand because your hand has blocked the light.has blocked the light.

– The shadows move The shadows move and change shape and change shape when you move your when you move your hand.hand.

Shadows Cont’dShadows Cont’d

• Light travels in straight lines. Light travels in straight lines.

• When you put your hand in front of a When you put your hand in front of a lamp, some of the straight lines of light hit lamp, some of the straight lines of light hit your hand. your hand.

• The shadow on the wall shows where the The shadow on the wall shows where the light is blocked by your hand.light is blocked by your hand.

• When you move your hand, the shadow When you move your hand, the shadow moves because your hand blocks different moves because your hand blocks different lines of light.lines of light.

Shadows Cont’dShadows Cont’d

• When you stand in the sun, you block When you stand in the sun, you block some of the lines of sunlight. some of the lines of sunlight.

• As the sun moves in the sky, you As the sun moves in the sky, you block different lines of light. In the block different lines of light. In the morning and afternoon, your shadow morning and afternoon, your shadow is long. is long.

• When the sun is high overhead, your When the sun is high overhead, your shadow is short.shadow is short.

Shadows Cont’dShadows Cont’d• Long ago, people figured Long ago, people figured

out that they could predict out that they could predict the pattern of changing the pattern of changing shadows during the day.shadows during the day.

• They used the pattern to They used the pattern to tell time. tell time.

• A device used to do so is A device used to do so is called a sun dial. called a sun dial.

• As the sun moves across As the sun moves across the sky, the shadow of the the sky, the shadow of the sun dial moves from left sun dial moves from left to right and points to the to right and points to the hours of the day.hours of the day.

ReflectionReflection• Reflection is the Reflection is the

bouncing of light off bouncing of light off an object.an object.– Light bounces from a Light bounces from a

mirror like a ball mirror like a ball bounces from a wall. bounces from a wall.

– If you roll a ball If you roll a ball straight at a wall, it straight at a wall, it bounces straight back bounces straight back to you. to you.

– If you roll a ball toward If you roll a ball toward a wall at an angle. a wall at an angle.

• Light strikes a mirror Light strikes a mirror at an angle and at an angle and bounces to your eyes.bounces to your eyes.

Reflection Cont’d Reflection Cont’d • Light bouncing off a Light bouncing off a

smooth surface gives an smooth surface gives an image you can see. image you can see. – A mirror is very smooth. A mirror is very smooth. – So are shiny metal and still So are shiny metal and still

water. water. – You can see yourself in You can see yourself in

these things. these things. • But most things aren’t as But most things aren’t as

smooth as mirrors. Most smooth as mirrors. Most things are bumpy. things are bumpy. – When light hits a bumpy When light hits a bumpy

surface, each straight line surface, each straight line of light goes off in a of light goes off in a different direction, so you different direction, so you can’t see an image.can’t see an image.

• A mirror can also A mirror can also have a smooth, have a smooth, curved surface. curved surface. Mirrors like this make Mirrors like this make your reflection seem your reflection seem bigger or smaller than bigger or smaller than you really are. you really are.

• Carnival fun houses Carnival fun houses and science museums and science museums often have such often have such mirrors on display.mirrors on display.

RefractionRefraction

• Refraction is the Refraction is the bending of light bending of light when it travels from when it travels from one kind of matter one kind of matter to another. to another.

• Refraction happens Refraction happens when light goes when light goes through a surface through a surface instead of instead of reflecting.reflecting.

Refraction Cont’dRefraction Cont’d• Refraction happens Refraction happens

because light travels because light travels at different speeds in at different speeds in air, water, and glass.air, water, and glass.

• If light hits new If light hits new matter straight on, it matter straight on, it keeps going straight. keeps going straight. But if light hits the But if light hits the new matter at a new matter at a slant, the light bends slant, the light bends or refracts. or refracts. – Ex. In line skater Ex. In line skater

dropping off concerete dropping off concerete onto grass onto grass

Refraction Cont’dRefraction Cont’d

• Examples of Examples of refraction:refraction:– Magnifying glassMagnifying glass– GlassesGlasses– Contact lensesContact lenses

Stopping LightStopping Light

• Absorption – When light hits an object Absorption – When light hits an object and is stopped or absorbed by the and is stopped or absorbed by the object.object.– Ex. Rain falling on grass is absorbed like Ex. Rain falling on grass is absorbed like

most matter absorbs light.most matter absorbs light.– When light hits most objects, some of the When light hits most objects, some of the

light bounces off and the rest is absorbed.light bounces off and the rest is absorbed.– Smooth, shiny objects reflect light.Smooth, shiny objects reflect light.– Other objects absorb most of the light that Other objects absorb most of the light that

hits them and reflect the rest. hits them and reflect the rest.

Stopping Light Cont’dStopping Light Cont’d

• Can you see your neighbor?Can you see your neighbor?– No, you can only see the light that is No, you can only see the light that is

being reflected off of him or her. You being reflected off of him or her. You can’t actually see your neighbor.can’t actually see your neighbor.

– Think about it, can you see your Think about it, can you see your neighbor if you turn off the lights?neighbor if you turn off the lights?

– Nope. There is no light being reflected Nope. There is no light being reflected off him or her.off him or her.

Stopping Light Cont’dStopping Light Cont’d

• There are three ways an object can There are three ways an object can interact with light. The light’s interact with light. The light’s interaction with an object is based on interaction with an object is based on what the object is made from.what the object is made from.– OpaqueOpaque– TranslucentTranslucent– TransparentTransparent

OpaqueOpaque

• An opaque object An opaque object reflects or absorbs reflects or absorbs all light. all light.

• If you try to look If you try to look through an opaque through an opaque object, you see object, you see only light reflecting only light reflecting from the object. from the object. – Ex. Wooden door, Ex. Wooden door,

ceiling, walls, floorceiling, walls, floor

TranslucentTranslucent• A translucent object A translucent object

reflects and absorbs reflects and absorbs some light. some light.

• You can see a blurry You can see a blurry or fuzzy image when or fuzzy image when you look through a you look through a translucent object.translucent object.

• Some light is Some light is reflected from the reflected from the object and goes object and goes through. through. – Ex. Plastic cup, Ex. Plastic cup,

fogged windowfogged window

TransparentTransparent

• A transparent object A transparent object does not reflect or does not reflect or absorb much light. absorb much light.

• You can see a clear You can see a clear image when you image when you look through a look through a transparent object. transparent object.

• Ex. Windows, plastic Ex. Windows, plastic wrap, colored or wrap, colored or clear glassclear glass

Ticket Out the DoorTicket Out the Door

1.1. How does light interact with a mirror?How does light interact with a mirror?2.2. Your shadow is shorter than you at 10:00 in Your shadow is shorter than you at 10:00 in

the morning. How do you predict its length the morning. How do you predict its length will change over the next two hours?will change over the next two hours?

3.3. Give an example of an object that is Give an example of an object that is opaque, translucent, and transparent. Tell opaque, translucent, and transparent. Tell whether each object reflects, absorbs, or whether each object reflects, absorbs, or reflects and absorbs light. reflects and absorbs light.

4.4. You stick your hand in an aquarium to get You stick your hand in an aquarium to get something out. Why does your arm look as something out. Why does your arm look as if it is broken?if it is broken?

Let’s ReviewLet’s Review• Light energy can cause things to change.Light energy can cause things to change.• Plants require light to make food.Plants require light to make food.• Some machines use energy from light to Some machines use energy from light to

generate electricity. generate electricity. • Light travels in a straight line unless it is Light travels in a straight line unless it is

reflected, refracted, or absorbed. reflected, refracted, or absorbed. • Mirrors produce clear images because their Mirrors produce clear images because their

surfaces are smooth. surfaces are smooth. • Bumpy surfaces don’t produce clear images.Bumpy surfaces don’t produce clear images.• Objects can be classified as opaque, Objects can be classified as opaque,

transluscent, or transparent based on how they transluscent, or transparent based on how they interact with light.interact with light.