Here’s a quick one day project I just finished.
I’m quite interested in light, and I wanted a quick way to observe how things change polarisation as light moves through them. You can pick up polariscopes on eBay pretty cheap, but in reality they’re not that complicated, and it’s pretty easy to make one yourself.
All you need is some polarising filter material (you can get here, there’s probably much cheaper ones available) and a way of holding it in place.
The only tricky bit is figuring out how to glue the filters so they’re aligned with the marks. We can use nature as a guide here.
We set up a lamp and a bowl of water at so the light reflects at roughly ‘Brewster’s Angle‘, and then rotate the filter and see when the reflection of the lamp is highest and lowest.
When vertically oriented, the reflection is minimised. (In this photo the 0* mark is correct).
When horizontally oriented, the reflection is maximized.
Once you’ve figured out how the filter plastic should be oriented, you can go ahead and glue it to the ring in the right place. Ideally I should have taken photos of me using the bowl and filter to find the orientation before gluing it to the wood ring, but I only realised afterwards. Basically if your filter rings behave like the above two photos, they’re correctly aligned.
So, project done! I’m pretty happy, and it should be easy for others to make as well.
Here’s a good resource if you’d like to learn how to use a polariscope:
And the files are up here for anyone that wants to make their own: