Light Powerpoint

Light and SoundIn this unit:

Properties of lightReflectionColoursRefractionProperties of soundHearing

Part 1 Properties of LightLight travels in straight lines:

Light travels VERY FAST around 300,000 kilometres per second.

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

Light travels much faster than sound. For example:

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 objectsA luminous object is one that produces light.A non-luminous object is one that reflects light.Luminous objectsReflectors

ShadowsShadows are places where light is blocked:

Properties of Light summaryLight travels in straight linesLight travels much faster than soundWe see things because they reflect light into our eyesShadows are formed when light is blocked by an object

Part 2 - ReflectionReflection from a mirror:Incident rayNormalReflected rayAngle of incidenceAngle of reflectionMirror

The Law of ReflectionAngle of incidence = Angle of reflectionIn other words, light gets reflected from a surface at ____ _____ angle it hits it.The same !!!

Clear vs. Diffuse ReflectionSmooth, shiny surfaces have a clear reflection:Rough, dull surfaces have a diffuse reflection.

Diffuse reflection is when light is scattered in different directions

Using mirrorsTwo examples:1) A periscope2) A car headlight

ColourWhite light is not a single colour; 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.

The colours of the rainbow:RedOrangeYellowGreenBlueIndigoViolet

Adding 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 againAdding red and green makes yellow

Seeing colourThe colour an object appears depends on the colours of light it reflects.For example, a red book only reflects red light:WhitelightOnly 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 lightWhitelight

Using coloured lightIf we look at a coloured object in coloured light we see something different. For example, consider a football kit:WhitelightShorts look blueShirt looks red

In different colours of light this kit would look different:RedlightShirt looks redShorts look blackBluelightShirt looks blackShorts look blue

Some further examples:

ObjectColour of lightColour object seems to beRed socksRedRedBlueBlackGreenBlackBlue teddyRedBlackBlueGreenGreen camelRedBlueGreenMagenta bookRedBlueGreen

Using filtersFilters can be used to block out different colours of light:

Investigating filters

Colour of filterColours that could be seenRedGreenBlueCyanMagentaYellow

RedMagentaWhiteYellowBlueGreenCyan

RefractionRefraction 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

Sound The basicsWe 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 soundsThis sound wave has a _____ frequency:This sound wave has a ___ _frequency:

Drawing soundsThis sound wave has a _____ amplitude (loud):This sound wave has a _____ amplitude (quiet):

Hearing problemsOur hearing range can be damaged by several things:

Too much ear wax!Damage to the auditory nerveIllness or infectionsOld age (not like Mr Richards)

Other sound effectsLike light, sound can be

Reflected sound reflections are called ______.Refracted this is why you might sound strange if you try talking underwater

The EarLabel your diagram with the following:

These bones are vibrated by the eardrum This tube carries the sound towards the eardrumThis part is used to help us keep our balanceThis part picks up the vibrationsThis part of the ear contains many small hairs with turn vibrations into an electrical signalThis part connects the ear to the mouthThis part channels the sound towards the ear drum

The Ear