Make Your Own *Really* Cheap Interferometer

Hello Everyone!

Welcome to another instructable by Let's Innovate.

In this instructable I will guide you to make your very own really cheap interferometer. Emphasis on the "really cheap" part because there are many costly kits out there you can buy but by following this tutorial you will be able to make your very own interferometer that will cost you nothing! And does not even require that much time to setup!

This project was part of my entry to the CAIE Science Project. I hope you find it interesting.

Don't know what an interferometer is? No problem, just check this out, this will get you really eager about these things: https://www.ligo.caltech.edu/page/what-is-interfer...

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Supplies

These are the things I used:

• 1 green laser pointer
• playdough
• 2 small mirrors
• 1 hardboard
• some pieces of wood(optional)
• Transparent plastic CD cover.
• Double sided Tape

Step 1: Getting a Laser!

I borrowed the laser from one of my friends. It is an expensive laser pointer and has a good focus but yours need not to be expensive. Those really cheap pointers from ebay will also work very well.

Like this one: https://www.ebay.com/p/Powerful-Green-Laser-Pointe...

Even those small keychain ones would work.

I would say to choose a green laser pointer, but any other colour will also work with no problems.

The laser pointer was cylindrical in shape and kept rolling over so I used some rubber bands and tied it to a piece of wood to add some elevation. You can use anything for preventing it from rolling like cardboard.

Step 2: Aligning the First Mirror

About the mirrors, I just cracked one small mirror(very carefully) into 2 usable small pieces and then glued them on some wood for stability.(Gluing them to wood is not important, you can use cardboard).

I then placed the hardboard down beside my laser pointer. After that I put some play-dough directly in front of the laser pointer. The mirror is placed over the play-dough now.

The next step is to turn on the laser pointer and tinker with the mirror so that the beam of light is directly reflected back into the lens of the laser.

You will notice that using play-dough helped a lot as it's soft and mushy nature easily gets deformed under the weight.

Step 3: The Beam Splitter

The most important part of a Michelson Interferormeter is perhaps it's beam splitter. Beam splitters are very expensive and are not easily accessible everywhere, so I made my own crude splitter.

The splitter is a cheap CD cover. Place it at an estimated 45 degree angle between the laser and mirror with some double sided tape. Make sure the split beam runs over the hardboard because the second mirror has to be placed on the hardboard.

The CD cover works flawlessly!

Step 4: Aligning the Second Mirror

This is the tricky part, but using the same technique of mighty play-dough, you can very easily get through.

Put some play-dough in the direction of the split beam. Now place the second mirror on the play-dough. Once again you need to adjust the mirror, but this time the reflected beam needs to directly hit back at where there is a bright light spot on the CD cover(beam splitter).

Once you have done this step you are ready to use this instrument!

Step 5: The Results!

Take your setup to a dark room and power up the laser. Look closely in the direction of interference (perpendicular to the first beam of light i.e. the laser and first mirror part, and directly in front of the second mirror). {You will need a wall to be close in the way of the direction of interference}.

You will see light and dark circles. It has a striking resemblance to water ripples doesn't it? This instrument uses light's wave properties to make accurate measurements.

Check this page out for more info: https://science.howstuffworks.com/dictionary/astro...

Just touch the mirror lightly the interference pattern will change. You can also just speak, and you will see changes on the interference pattern. This instrument is highly sensitive and it was used to discover gravitational waves.

Check out LIGO: https://www.ligo.caltech.edu/

You have just made your very own precisely measuring tool for very cheap. You can also shift the mirrors forward and backward and make distance measurements in wavelengths. This tool can also be used to check lenses. What you can do with this tool is limitless, so make your own quick!