Exploring Optic Principles through Visual Tricks

Libby Sutton

Laser Teaching Center
Stony Brook University


Introduction

This project came about after months of exploring different topics and stumbling upon a paper written by a Professor John Howell from University of Rochester and his son. This paper explored three different ways of optical cloaking without metamaterials. Though this explored optical cloaking, we can use simple optical tricks to make objects move, distort, and disappear. In this project, we explored several toys and demonstrated how refraction and reflections are used in each one to achieve different effects. Several toys or objects that we explored was the 'Mirage' Toy, Van Gogh Vodka bottle,' Shake your Own Hand' mirror, angled mirrors, and demonstrated one of Howell's cloaking devices using a tank filled with water.

Mirage Toy

Many students in the past have explored the 'magical' properties of the Mirage Toy. This toy makes a real image of any object placed inside of it to be produced on the toy's lid, which in this case is a pig. The 'Mirage' is made up two parabolic mirrors with one of them having a hole cut out of its center. These mirrors are then placed on top of each other which is actually equal to one focal length of each mirror. Through ray optics, we see that the parabolic mirrors reflect the light in such a way that the rays converge at the apex/hole of the top mirror. Where all these rays converge is where our real image is produced. What is very interesting and is explored in this earlier project is that the more focal lengths apart the mirrors are the more real images that are produced. These images become more diffuse as the we add more focal lengths due to escaped rays.


Van Gogh Bottle

This vodka bottle no longer holds its liquor but it does create a great cylindrcal lense. Images of Van Gogh's paintings are stretched on the middle of the bottle. When water is filed and the bottle is upright, a cyclindrical lens, is created that compresses in the image into more normal proportions.


'Shake your own Hand' Mirror

The 'shake your own hand' mirror uses a concave mirror to make it seem like you can shake your own hand. The way the mirror reflects light and depending on where an object is placed, the reflections produced can have many properties. When an object is located at the center of curvature of the mirror the image produced is the perfect reverse image of your hand or its 'mirrored image'. As an object gets closer and closer to the center of the mirror, the image starts to fill the entire sphere while the opposite occurs as you pull it away.


Angled Mirrors

Angled mirrors can have amazing properties that are directly related to the angle at which they are set to one another. At a right angle, three images are formed and the central image is actually how others see you due to the reflection properties. As the angle decreases, the number of images increase to infinity when the mirrors are parallel to one another.


Howell Tank Simulation

Howell created an experiment using two L shaped tanks that was capable of cloaking a small region between them. The device does this mainly by utilizing Snell's Law. As light enters the device, it gets refracted away from the center until hitting the outer edge of the tank where it is then bent back parallel to the incident ray. This occurs again at the next tank except that the incident rays are bent inward then bent back. This trick allows us to see an object behind the tanks, while hiding the object in between them.

We can demonstrate the simple principles he uses using just a single tank filled with water. Using this tank we were able to displace the image of a flashlight and a rod as to make it appear that the flashlight was actually where the rod was located. As the light goes through the angled tank, it is bent closer to a normal line in the diagram. Once it hits the other edge of the tank it is bent back to its original orientation because of the difference in indices of refraction. This makes the image of the flashlight base appear to be where the rods base originally was.


Acknowledgements

None of this project would have been possible without Dr Noé and the advice and help from my peers. I can't thank them enough for their help and for teaching me so much this semester.