Light and SoundLight and Sound

In this unit:

1) Properties of light2) Reflection3) Colors4) Refraction5) Properties of sound6) Hearing

What is light?What is light?

Light is a kind of energy.

Without light energy you could not see anything!!!!!!!!

Light energy gives things colors, helps plants to grow, can power solar batteries to make electricity and is used in lasers.

Part 1 – Properties of Part 1 – Properties of LightLight

Light travels in straight lines:How does the following

experiment prove this??????

Laser

Shadows

Shadows are places where the straight lines of light are “blocked”:

Rays of light

Light travels VERY FAST – around 300,000 kilometers per second.

At this speed it can go around the world 8 times in one second.

Light travels much faster than sound. For example:

1) Thunder and lightning start at the same time, but we will see the lightning first.

2) When a starting pistol is fired we see the blast first and then hear the bang.

We see things because they reflect light into our eyes:

Homework

Luminous and non-luminous objects

A luminous object is one that produces light.

A non-luminous object is one that reflects light.

Luminous objects Reflectors

Properties of Light Properties of Light summarysummary

1) Light travels in straight lines2) Light travels much faster than sound3) We only see things because they

reflect light into our eyes4) Shadows are formed when light is

blocked by an object5) Light is a form of energy like heat and

electricity

Part 2 - ReflectionPart 2 - ReflectionReflection from a mirror: What do you notice about

where the mirror puts the light you shine into it?

Incident ray

Normal

Reflected ray

Angle of incidence

Angle of reflection

Mirror

The Law of ReflectionThe Law of Reflection

Angle of incidence = Angle of Angle of incidence = Angle of reflectionreflection

In other words, light gets reflected from a surface at ____ _____ angle it hits it.

The same !

!!

Clear vs. Diffuse ReflectionClear vs. Diffuse Reflection

Smooth, shiny surfaces have a clear reflection:

Rough, dull surfaces have a diffuse reflection.

Diffuse reflection is when light is scattered in different directions

Absorbing LightAbsorbing Light

Stopping light is called absorption. When light hits most objects, some of the

light bounces off and the rest is absorbed.

Smooth shiny objects reflect most of the light. Dull objects absorb most of the light that hits them an reflects the rest.

What you see when you look at it is the light that bounces off of it.

AbsorptionAbsorptionOpaque Objects-Reflects or absorbs all the light.

You cannot see through opaque objects. Can you name some opaque objects?

Translucent Objects-Reflects and absorbs some light. You can see a blurry or fuzzy image when you look through it. Can you name some opaque objects?

Transparent- Does not reflect or absorb light. You see a clear image when you look through it. Can you name some transparent objects?

Using mirrorsUsing mirrorsMirrors reflect all the light!Two examples:

1) A periscope

2) A car headlight

ColorColor

White light is not a single color; it is made up of a mixture of the seven colours of the rainbow.

We can demonstrate this by splitting white light with a prism:

This is how rainbows are formed: sunlight is “split up” by raindrops.

Prisms bend or refract light!

The colors of the rainbow:The colors of the rainbow:

RedOrangeYellowGreenBlue

IndigoViolet

Adding coloursAdding coloursWhite light can be split up to make separate

colours. These colours can be added together again.

The primary colours of light are red, blue and green: This is different than paint primary colors!!!

Adding blue and red makes magenta (purple)

Adding blue and green makes cyan

(light blue)

Adding all three makes white again

Adding red and green makes yellow

Seeing colorSeeing colorThe color an object appears depends on the

colors of light it reflects.

For example, a red book only reflects red light:

White

light

Only red light is

reflected

A white hat would reflect all seven colors:

A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and

blue):

Purple light

White

light

Using colored lightUsing colored light

If we look at a colored object in colored light we see something different. For example, consider a football kit:

White

light

Shorts look blue

Shirt looks red

In different colors of light this kit would look different:

Red

lightShirt looks red

Shorts look black

Blue

light

Shirt looks black

Shorts look blue

Some further examples:

Object Colour of lightColour object seems to be

Red socks

Red Red

Blue Black

Green Black

Blue teddy

Red Black

Blue

Green

Green camel

Red

Blue

Green

Magenta book

Red

Blue

Green

Using filtersUsing filtersFilters can be used to “block” out different colours of

light:

Red Filte

r

Magenta

Filter

Red

Magenta

White

Yellow

Blue Green

Cyan

Refraction Refraction ((http://http://www.brainpop.com/science/seeallwww.brainpop.com/science/seeall/)/)

Refraction is when waves ____ __ or slow down due to travelling in a different _________. A medium is something that waves will travel through. When a pen is placed in water it looks like this:

In this case the light rays are slowed down by the water and are _____, causing the pen to look odd. The two mediums in this example are ______ and _______.

(Words – speed up, water, air, bent, medium)

THE LENSTHE LENS

CONVEX-BICONVEXCONVEX-BICONVEXConvex Lenses

cause light toconverge

or come together because one or

both sides curve outward.

Looking through a convex lens make things

look: ????

CONCAVE-BICONCAVECONCAVE-BICONCAVE

Concave Lenses cause light toconverge or come together. Looking through a convex lens make things look:

THE LENS YOU USE THE LENS YOU USE EVERYDAYEVERYDAY

Sound – The basicsSound – The basics

We hear things when they vibrate.

If something vibrates with a high frequency (vibrates very ______) we say it has a _____ pitch.

If something vibrates with a low frequency (vibrates ______) we say it has a ____ pitch.

The lowest frequency I could hear was…

Words – slowly, low, high, quickly

Drawing sounds…Drawing sounds…

This sound wave has a _____ frequency:

This sound wave has a ___ _frequency:

Drawing sounds…Drawing sounds…

This sound wave has a _____ amplitude (loud):

This sound wave has a _____ amplitude (quiet):

Hearing problemsHearing problems

Our hearing range can be damaged by several things:

1) Too much ear wax!

2) Damage to the auditory nerve

3) Illness or infections

4) Old age (not like Mrs. Powers)

Other sound effects…Other sound effects…

Like light, sound can be…

1) Reflected – sound reflections are called ______.

2) Refracted – this is why you might sound strange if you try talking underwater

The EarThe Ear

Label your diagram with the following:

These bones are vibrated by the eardrum

This tube carries the sound towards the eardrum

This part is used to help us keep our balance

This part “picks up” the vibrations

This part of the ear contains many small hairs with turn vibrations into an electrical signal

This part connects the ear to the mouth

This part “channels” the sound towards the ear drum

The EarThe Ear