What is a rainbow?
Transcript
Rainbows form striking arcs of colour across the sky.
They can seem to form unexpectedly.
But two things are always needed to create a rainbow.
formation of rainbows
Sun low in sky
water in the air
The Sun needs to be low in the sky and there needs to be water in the air.
A rainbow is an arc of light separated into the different colours that make up the Sun's white light.
white light
White light is split into these colours by drops of mist or rain.
Light travels more slowly through water than air.
So when light passes from air into a water droplet, it slows down.
This makes the light bend and change direction.
This bending is called refraction.
refraction
bending of light
As the white light refracts it separates into the colours of the rainbow.
Red, orange, yellow, green, blue, indigo and violet.
The light bounces off the back of the water droplet and is reflected back into the air.
reflected
As it leaves the water, the light is refracted once again.
The different colours are bent by different amounts.
Those at the violet end of the rainbow bend more than those at the red end.
This is what gives the rainbow its arched shape.
However hard you try, you can never get close to a rainbow.
As you move towards it, another set of raindrops create the same pattern of light further away.
white light
refraction
reflection
Rainbows look beautiful in the sky.
But you don’t see them often.
A rainbow only forms when:
rainbow forms when:
Sun low in the sky
water in the air
the Sun is low in the sky…
and there is water in the air.
A rainbow is an arc of light. White light from the Sun has been separated into different colours.
white light
White light is separated by drops of water.
Light travels more slowly through water than air.
So when light passes from air into a water droplet, it slows down.
The light bends and changes direction.
The bending of light is called refraction.
refraction
bending of light
When the white light refracts, it separates into the colours of the rainbow:
red, orange, yellow, green, blue, indigo and violet.
The light bounces off the back of the water droplet and is reflected back into the air.
reflected
As it leaves the water, the light is refracted again.
The different colours are bent by different amounts.
Violet light bends more than red light.
This is why the rainbow is an arc.
You can try, but you will never get close to a rainbow.
When you move towards it, different raindrops make the same arc of light further away.
white light
refraction
reflection
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