Information about How can icebergs be blue with Fizzics Education | Kids Science Experiments

# How can icebergs be blue and why is this related to sunsets?

Follow FizzicsEd 150 Science Experiments:

You will need:

One large clear container filled with 5 litres of water

Milk

A strong source of light, eg. spotlight, projector lamp

A darkened room

1

Pour about 100ml of milk into the water. It is often best to use only a little at first. Try the following steps out and only add more if the intended effects is not apparent.

2

Turn the spotlight on and darken the room

3

Turn the light to face the milky water.

4

The water near the milk will look white, yet if you look on the other side of the container the colour should be a mixture of orange and red. Something has been happened to the light as it passes through the milk solution.

### Why Does This Happen?

The demonstration just performed is a classic way of showing how sunsets work. White light is comprised of all of the colours of the rainbow i.e. the light spectrum. The different colours you see represent the different wavelengths of light.

An orange object is only ‘orange’ when you see the orange wavelength of light being reflected off it.

When light travels through a substance, some of the visible light wavelengths are absorbed whilst the other light is reflected. As the light entered the milk solution the light in the blue end of visible spectrum was scattered by the suspended milk solids. This left the lower energy wavelengths of orange and red to pass through the solution, creating the orange/red colour seen in the experiment.
So how does this relate to sunsets?

The daytime sky appears blue because this blue light is scattered more readily towards us, known as Rayleigh scattering. During sunset the sunlight is still scattered, however the blue light is scattered away from our eyes leaving the oranges and reds you see.

So how does this relate to blue icebergs?

In an average iceberg there are large amounts of trapped air bubbles. The air scatters the light passing through the iceberg and all the visible wavelengths of light toward you, making it appear white.

However, an iceberg formed under water, away from the air, will have little to no air bubbles within it.
Passing light through such an iceberg will have the weaker red wavelength of light be absorbed by the ice, leaving the more high energy blue light to pass through the iceberg and into your eye, and so you see it as being blue.
Note: Mixing coloured light together always makes white; this is known as colour addition.

### Learn more!

Teaching about light absorption & reflection? From Light & Colour workshop has you covered!
Get in touch with FizzicsEd to find out how we can work with your class.

### Comments

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