Smartphone Polariser Mosaic
By Ollie
In this laboratory session, we will make a fun stained-glass style visual effect, using some household items and a smartphone.
This is a very simple experiment which you can do with just a pair of old 3D glasses, some scotch tape, and pretty much any screen you have in your home.
​
This page will give you some useful information about how the lab works, and what you will need to complete it.
What do I need to prepare?
Smartphone
You can use pretty much any screen for this, but if you have a smartphone handy, that'll work great!
Scotch tape / sellotape
The basic plastic see-through tape you can buy anywhere
3D glasses
We mean the type of 3D glasses that were popular about 10 years ago - the passive ones that look like sunglasses, not the red and blue ones.
Smartphone Polariser Mosaic Instructions
1. Collect your phone, sellotape, and 3D glasses
You can use any type of see-through tape for this, but the 3D glasses need to be the passive type that look like sunglasses, rather than the red and blue type.
​
Make sure you won't need the 3D glasses in the future. This experiment will not damage the glasses, but you will be sticking some tape to the lenses which may leave some residue.
2. Layer your sellotape on your glasses
You are going to want to take some sellotape, and tear it off in thin strips. Then you can layer these strips onto your glasses.
​
You can try a simple design at first, maybe just a criss-cross pattern or some simple lines. Try to arrange them in different shapes. You won't see any effect at the moment, until we look at a screen with them.
3. Look at your phone screen through your glasses
Get a white background up on your phone, and look at the screen. If you look through the sellotape at your phone screen, you should see all kinds of different colours. Now rotate the glasse, and the colours will change into a cool mosaic pattern. Interesting right?
4. Try looking at other screens
This should work on most types of screens in your house, but there may be minor differences in how the affect appears. Older screens may go completely black when you rotate the glasses.
5. Try looking at something made of plastic
Turn off the lights and look at your phone screen, with a plastic bottle in front of it, through your 3D glasses. You should see a cool rainbow effect!
How does this work?
How do 3D glasses work?
To explain how this works we have to understand how 3D glasses work.
When you go to see a 3D movie, the cinema projector is actually projecting two movies onto the screen, which are both differently polarised. When we talk about polsarisation, we mean the angle at which the light is oriented. Each lens of your 3D glasses contains a polarizing filter which allows one direction of light to enter, blocks the light polarised in the other direction. This means that each eye sees a different image, creating the illusion of depth.
So what does the tape do?
The sticky side of sellotape is sticky because of adhesives which are deposited along the length of the tape. These adhesives cause the light polarised along the direction that the adhesives are layed to travel through the tape more slowly than light polarized perpendicular to the adhesive.
The colors you see are caused by changes in the speed of polarized light as it travels through the adhesive on the tape. The polarisation of each colour will change by different amounts as it passes through the tape, meaning that varying amounts of each colour are blocked out at each angle that the 3D glasses are held.
Why does my smartphone screen change the colours?
Manufacturers install polarising filters as part of phone screens, in order to cut down on reflective glare when using the phone. The polariser reduces the amount of light that will be reflected off the screen, for example by the sun, which might make it difficult to see the screen.
This is why it can sometimes be difficult to use a smartphone while wearing polarised sunglasses. Because the light here is polarised, the tape on the glasses will allow different amounts of each colour to pass through at different angles.
Older smartphones or LCD screens may look different during this experiment than newer screens, because they use linear polarisers, rather than circular polarisers. If you have an old LCD screen, try turn your glasses to a certain angle, you may be able to block out the image from the screen completely!
Why does the plastic bottle make the rainbow effect?
The rainbow effect occurs because the plastic is made of a polymer which is set in a range of different alignments. Changes in these alignments and differences in thickness cause the polarised light to take different amounts of time to pass through the object. When the light exits the object, the light rays interfere, causing the rainbow effect. This is similar to the rainbow pattern you sometimes see in soap bubbles.
