Light and SoundLight and Sound

In this unit:

1) Properties of light2) Reflection3) Colours4) Refraction5) Properties of sound6) Hearing

Part 1 – Properties of Part 1 – Properties of LightLight

Light travels in straight lines:

Laser

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 smoke 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

Shadows

Shadows are places where light is “blocked”:

Rays of light

Energy in LightEnergy in Light

-There is a lot of energy in light.-For example, when you stand in the sun you

feel the sun’s energy through heat.-If you absorb too much of that energy, you

can get a sunburn.-A lamp doesn’t have as much energy as the

sun- you can’t get sunburned by a lamp.-However, a lamp does give off heat because

of the electric current it takes to make it work.

Properties of Light Properties of Light summarysummary

1) Light travels in straight lines.2) Light travels much faster than sound.3) We see things because they reflect

light into our eyes.4) Shadows are formed when light is

blocked by an object.5) Light gives off energy in the form of

heat.

Part 2: ReflectionPart 2: Reflection-When light hits an object, the object affects the

path of the light.-An object can absorb light, make it bounce off,

or let it pass through.-Some light energy is absorbed. Darker objects

absorb more light energy-that’s why you are hotter when you wear dark colors on a hot day.

-Objects don’t absorb all the light that hits them. Some of the light bounces off. Reflection is the bouncing of light from a surface.

Part 2:ReflectionPart 2:Reflection

-Usually, light scatters in many directions when it is reflected.

-A smooth surface reflects light in a clear and predictable pattern.

-Have you ever seen a reflection in clear windows on a building?

-Looking in a mirror can also get you a smooth reflection, but it gives you a backward image.

Reflection from a mirror:

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 !

!!

RefractionRefractionWhen light moves from water to air, its speed changes. The change in speed makes the beam of light bend. This bending of light is called refraction. Refraction is bending light.

When a pen is placed in water it looks like this:

Refracted light can make a solid object look like it is broken into two parts. It looks like that because the light from the part of the pencil that is under the water reaches your eyes on a different path.

Translucent MaterialsTranslucent Materials

-Materials that let some light through are called translucent. An example of a translucent material is a frosted light bulb.

Transparent MaterialsTransparent Materials

-A transparent material allows most of the light that hits it to pass through it.-Most glass, water, and some plastics are transparent.-Transparent objects don’t scatter light, but they do refract it.

Opaque MaterialsOpaque Materials-Materials that do not allow any light to pass through them are opaque.-Opaque materials absorb all the light into them.-Metal, wood, and most of your body is opaque.

ColorColor

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

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

Light and ColorLight and Color-As light enters a prism, the light waves change directions and separate (this is an example of refraction).-You are able to see all the colors of the rainbow when the colors separate.-You can remember all the colors of the rainbow with ROYGBIV.-When have you seen a rainbow of color?

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

RedOrangeYellowGreenBlue

IndigoViolet

LensesLenses-A lens is a curved, transparent object that refracts light.-There are different types of lenses with different types of curves.

Convex LensConvex Lens

-A convex lens is thicker in the middle than at the edges.-As light waves move through the lens, they bend towards the thickest part-the middle.-A convex lens makes light waves come together and make objects appear larger or magnified.

Concave LensConcave Lens-A concave lens is thicker at the edges than in the middle.-As light waves enter the lens, they bend toward the thicker part- the ends.-The concave lens makes light waves spread out and this makes objects appear smaller.

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: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 colourSeeing colourThe colour an object appears depends on the

colours 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 colours:

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 coloured lightUsing coloured light

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

White

light

Shorts look blue

Shirt looks red

In different colours 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

Investigating filtersInvestigating filters

Colour of filter Colours that could be “seen”

Red

Green

Blue

Cyan

Magenta

Yellow

Red

Magenta

White

Yellow

Blue Green

Cyan

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 Mr Richards)

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