Is a form of energy

Why is light important?  Photosynthesis  Electrical energy  Heat  To live!

What else can light do?  It can be converted into other forms of energy  For example:  Solar power – electrical  Heat energy  Chemical energy - photosynthesis

No sun No light bulbs No fires or candles

Light travels in waves

Light travels very fast! The speed of light is 300,000,000 metres per second

It takes light from the sun 8 minutes to reach earth The Sun is approximately 93 million miles from Earth!! How long to you think it would take to drive that distance in a car?

106 YEARS!!! Lets presume he drives at 100mph

Light travels in straight lines!

What examples are there to prove this???

How can we prove this?

Mandatory Experiment  To show that light travels in straight lines. 1. Take three pieces of cardboard. 2. Place a hole in the centre of each. 3. Place the apparatus as shown in the diagram.

Luminous and non-luminous objects  Luminous objects give out the own light  Examples?? Light filamentThe Sun

Non – luminous objects  Reflect light!  example??  Your books  Your chair  Your table

Now a tricky one  Is a light bulb non - luminous?  40-out-of-darkness-reflection-and- luminosity-video.htm

COLOUR Imagine you could only see in black and white. What are the possible implications this could have on your life? Would it rule out any careers for you? What dangers could there be?

What has colour got to do with light?!

1.Shine a ray of bright white light at a prism, as shown above, and move the prism until colours appear. 2.Draw a diagram to show what your observed. White light is split up into 7 colours ???????

The white light splits up into 7 colours called the...

Where have you seen this before??  Rainbow  CD  Oil on the ground  The sky??

R.O.Y.G.B.I.V  RED  ORANGE  YELLOW  GREEN  BLUE  INDIGO  VIOLET

Until now we have used the title ‘splitting white light up’. However this process has a scientific name. The splitting of white light into a spectrum of colours is called DISPERSION. But why does white light get dispersed? Colour : splitting white light up

Dispersion Each of the colours [ROYGBIV] has a slightly different waveform - what is different? They each have a different wavelength [ ].

Primary Colours of Light

REFLECTION

What makes a good reflector?? Any example of a really good reflector?

What do we notice about reflection?  Light bounces back  Lateral inversion

DogManBall BatBikeAnts ParkFinsPink LitterSandyShark

To investigate the reflection of light by a PLANE MIRROR

Mirror Light Beam ir

 ection1.htm

Uses of Reflection?!

 om/photos/abysp here/ / om/photos/abysp here/ /

Periscope!

Refraction

Refraction is the bending of light when it moves from one medium to another

Refraction : Bending light The speed of light waves depends on the material they are travelling through. If the light waves enter a different material [e.g. from glass into air] the speed changes. This causes the light to bend [or refract]. Air = FastestDiamond = slowestGlass = slower Glass

Fast and slow  If you were running along a beach and then ran into the water when would you be moving slower, in the water or on the beach? In a similar way as light moves from one medium to another of different density the speed of light changes. Do you think light moves faster or slower in a more dense medium? Light moves slower through a more dense medium.

Refraction - at the air-glass boundary

To show the refraction of light as it passes from air to glass 1. Pass a ray of light from a ray box into a block of glass on a white sheet of paper. 2. Note the direction of the light rays outside and inside the glass. 3. Make an outline of the block of glass. 4. Trace the ray of light using a pencil. 5. Finish the ray diagram and label. 6. Write up experiment in your lab copy

Ray box Glass block Ray of incidence Ray of refraction??

Refraction in a Block of Glass Incident Ray Refracted Ray I R Block of Glass

Result?  Your ray diagram should show the refraction of light.

Refraction in a rectangular block

eo.php?video_id=107400&title= bill_nye_the_science_guy___refr action_2_3

APPLICATIONS OF REFRACTION LENSES A LENS IS A PIECE OF TRANSPARENT MATERAIL THAT HAS A LEAST ONE CURVED SURFACE

Investigate how light is refracted through these lenses.  Set up apparatus.  Place ray diagram at end of paper and shine light ray through the lens.  Trace the path of refraction on the sheet of paper.  Outline the shape and position of the lens.

note!  Use fine three ray slide.

(Draw ray diagrams)

Uses of a lens