LIGHT ! from bonfires to lasers

Sources of light Hot objects give out light. A bonfire

Hot objects give out light.

The Sun Sunset in Venice

Sunset in Venice

Stars Stars and galaxies give out light. Picture: Liverpool Telescope

Stars and galaxies give out light.

Lightning

A worm living in dark caves sends out light from its tail. Liquid droplets form a string of shining beads to attract insects. tail of worm

Liquid droplets form a string of shining beads to attract insects.

Some cold things give out light: some fungi glow worms light sticks LEDs ‘glow-in-the-dark’ stickers

some fungi

glow worms

light sticks

LEDs

‘glow-in-the-dark’ stickers

How do we see light sources? Light travels from a source to our eyes. We can see sources in a dark room.

Light travels from a source to our eyes.

We can see sources in a dark room.

Can we see in the dark? If there is no light we cannot see anything! Let’s try a test– Put a few small objects into the black bag-----

If there is no light

we cannot see anything!

Let’s try a test–

Put a few small objects into the black bag-----

How do we see things that are not sources of light? Light bounces off and some reaches our eyes.

Light bounces off

and some reaches our eyes.

On the look out ! How do you know that the baby squirrel watches as it feeds?

How do you know that the baby squirrel watches as it feeds?

Reflection When light bounces off something we say the light is reflected . We can try this with rough surfaces and shiny surfaces.

When light bounces off something

we say the light is reflected .

We can try this with

rough surfaces

and shiny surfaces.

Shiny surfaces Light is reflected as a beam and can be seen on the wall. mirror wall

Light is reflected as a beam and can be seen on the wall.

Move the mirror The light reaches a different place on the wall. wall

The light reaches a different place on the wall.

Look in a mirror Light is reflected. You can see a reflection.

Light is reflected.

You can see a reflection.

Change the direction of the light beam Light is still reflected. You see a reflection - in a different direction.

Light is still reflected.

You see a reflection

- in a different

direction.

Multiple reflections The lamp hangs between two large mirrors on opposite walls. The reflection in the first mirror is reflected in the second mirror, which is reflected again in the first mirror - - -

The lamp hangs between two large mirrors on opposite walls.

The reflection in the first mirror is reflected in the second mirror, which is reflected again in the first mirror - - -

Now for some games !

Colour

Sunlight shining on CDs Where do the colours come from?

Where do the colours come from?

Rainbow red orange yellow green blue indigo violet

red

orange

yellow

green

blue

indigo

violet

Colours White light is made up of lots of colours

White light is made up of lots of colours

Colours from white light Look at a lamp through the grating. You will see colours.

Look at a lamp through the grating.

You will see colours.

red

red

blue

blue

Adding colours with light This is different to adding paints

This is different to adding paints

Red + Blue  magenta

Blue + Green  cyan

 cyan

Green + Red  yellow

 yellow

yellow

yellow

magenta

cyan

Fairy lights

Uses Lasers- produce very bright beams of light. The atoms all give out their light together CDs use laser light and reflection-

Lasers- produce very bright beams of light.

The atoms all give out their light together

CDs use laser light

and reflection-

CDs The surface has tiny pits and smooth bits in a spiral pattern the pits scatter light from a laser the smooth bits reflect the light so a coded message is read. spiral

The surface has tiny pits and smooth bits

in a spiral pattern

the pits scatter light from a laser

the smooth bits reflect the light

so a coded message is read.

Laser show Physics is in everything

Physics is in everything