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Light presentation

May 18, 2015

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Satyam Gupta

it is a 9 and 10 th presentation its good for people and i can wet you will get a1 if you download from here.
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Page 1: Light presentation
Page 2: Light presentation

Light and SoundLight and Sound

In this unit:

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

Page 3: Light presentation

Part 1 – Properties of Part 1 – Properties of LightLight

Light travels in straight lines:

Laser

Page 4: Light presentation

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

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

Page 5: Light presentation

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.

Page 6: Light presentation

We see things because they reflect light into our eyes:

Homework

Page 7: Light presentation

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

Page 8: Light presentation

Shadows

Shadows are places where light is “blocked”:

Rays of light

Page 9: Light presentation

Properties of Light Properties of Light summarysummary

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

light into our eyes4) Shadows are formed when light is

blocked by an object

Page 10: Light presentation

Part 2 - ReflectionPart 2 - ReflectionReflection from a mirror:

Incident ray

Normal

Reflected ray

Angle of incidence

Angle of reflection

Mirror

Page 11: Light presentation

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 !

!!

Page 12: Light presentation

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

Page 13: Light presentation

Using mirrorsUsing mirrorsTwo examples:

1) A periscope

2) A car headlight

Page 14: Light presentation

ColourColour

White 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.

Page 15: Light presentation

The colours of the rainbow:The colours of the rainbow:

RedOrangeYellowGreenBlue

IndigoViolet

Page 16: Light presentation

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

Page 17: Light presentation

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

Page 18: Light presentation

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

Page 19: Light presentation

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

Page 20: Light presentation

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

Page 21: Light presentation

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

Page 22: Light presentation

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

light:

Red Filte

r

Magenta

Filter

Page 23: Light presentation

Investigating filtersInvestigating filters

Colour of filter Colours that could be “seen”

Red

Green

Blue

Cyan

Magenta

Yellow

Page 24: Light presentation

Red

Magenta

White

Yellow

Blue Green

Cyan

Page 25: Light presentation

RefractionRefraction

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

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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

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Drawing sounds…Drawing sounds…

This sound wave has a _____ frequency:

This sound wave has a ___ _frequency:

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Drawing sounds…Drawing sounds…

This sound wave has a _____ amplitude (loud):

This sound wave has a _____ amplitude (quiet):

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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)

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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

Page 33: Light presentation

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

Page 34: Light presentation

The EarThe Ear