Tag Archives: Optics

To Infinity Table and Beyond

Light, it’s properties, and the ways it can be manipulated are as fascinating as they are beautiful. It can be bent, slowed down, absorbed, and reflected. It turns out that the study of optics looks into all of these different interactions. But what happens when you want to mix the science of optics with a bit of real-world fun? You get an infinity table!

Infinity tables are named as such due to the illusion that the lights go on forever down into the depths of the table. But how can that be?

Infinity Table

To answer this, you not only need to know how the table was made, but also what optical properties those materials have. The three materials that makes these tables unique are LED lights, a normal mirror, and a two way mirror. The LEDs of course provide the visually pleasing light source. The normal mirror on the bottom of the table allows for the light to be completed reflected back up. And finally, the two way mirror allows for half of the light to escape the box of the table, and the other half to be reflected back down.

Because half of the light can escape through the two way mirror, with each bounce, half of the light is lost from the box. This is how the light appears to grow dimmer as you look down further into the apparent depths of the table.

Infinity Table 1

These tables are not the easiest to make at home, however it is not impossible. A simple home goods store may have all of the supplies needed. Just be sure to have adult help and supervision if you are to attempt this, given that glass is involved.

Written By: Mimi Garai

DIY: 3D Hologram

Have you ever wanted to feel like you exist in a Sci-Fi world? Or make something that just seems impossible? With this DIY 3D Hologram you can! It is a simple at-home craft that will dazzle your friends and family.

3D Hologram

All you will need:

  • Printable template
  • Transparency sheet
  • Scissors  
  • Marker
  • Ruler
  • Smartphone or tablet

3D Hologram 1

Step 1: Trace the template using your marker and ruler.

Step 2: Make the cuts to your transparency sheet.

Step 3: Fold the edges to form a pyramid.

Step 4: Find an awesome 3D video online for your smartphone or tablet to project.

Step 5: Place the pyramid in the center of your device, get down to the same level as the device, watch, and enjoy!

It’s as simple as that to transform your ordinary device into an out-of-this-world experience. But how does it work?

3D Hologram bird

Optics is all about the manipulation of light with lenses, mirrors, and splitters. Light can bend, get absorbed, and reflect. When watching the video on your device, the light being emitted from the screen is mostly aimed straight up. Once the pyramid is added, the plastic that hangs over the images acts as a splitter. It allows light to both travel through it and get reflected at the same angle at which it enters. The four different sides will add the four images into the center, creating what looks like a 3D hologram!

3D Hologram world

We had way too much fun creating this 3D hologram projectors. Be sure to give this a try and let us know what you think!

Written by: Mimi Garai

 

Hiding from Thermal Vision

Thermal cameras operate by looking at objects in a different band of light called infrared, which is the way heat transmits. Ordinarily, you could see a person from behind a wall or other solid object by looking in the infrared, as their heat still passes through that object somewhat, like with the garbage bag (DO NOT TRY THAT AT HOME).

 

In the case of plexiglass and glass, however, infrared light is not able to pass through, resulting in a blank spot where Jacob’s head and hand used to be. You can even see it with Jacob’s glasses, as they are cooler than most of his face in the infrared.

 

We actually use this property of plexiglass here at AstroCamp for several solar-powered devices. The inside of our solar ovens are black so they absorb visible light, heating up, and have a plexiglass door covering them so that heat can’t escape. We also use this for a solar water heating system where visible light strikes a black metal tube, which heats up and conducts heat well, then that heat is trapped by a plexiglass covering. Our IR camera is a great source of learning, but it’s also just a lot of fun.

Groundhog Phil’s Got Nothing On These Shadows

While the eyes of Punxsutawney, Pennsylvania are focused on the shadow of a groundhog. We here at AstroCamp have different shadows in mind. Using red, green, and blue lights, we’re making up to seven different shadows at once!

The key to these shadows is the different lights, both their colors and their positions. Red, green, and blue are often referred to as the primary colors of light, as those three colors can be combined in different amounts to produce any other color of light. The most common of these combinations are red and blue to create magenta, red and green for yellow, blue and green for cyan, and all three primary colors to create white light. Now, if we were to just shine a magenta light at someone’s hand, they would still only show the normal shadow we’re used to. This is because a shadow is simply the absence of light, and all the light is coming from one direction. However, if we place the red and blue lights at different points and then angle them to mix into magenta light, we see the normal black shadow, as well as red and blue shadows!

These different color shadows exist because the hand blocks the blue light coming from one angle, which the red light still fills in to create a red shadow, and the reverse is true for the red light being blocked to create a blue shadow. There is still some space in the middle, however, where both lights are blocked, allowing us to still have the traditional shadow. This same concept applies to cyan, yellow, and white light, as you can see below.

You might notice something different about the shadows in the most recent picture, with good reason. When shining all three primary colors at an object, you can see yellow, cyan, and magenta shadows as well. These shadows are due to the same principle as before, but exist in spots where one color of light is blocked and both of the others can continue unimpeded and mix together. Try this at home for some of the coolest shadow puppets ever!

Refraction: How To Bend a Laser Beam

Light travels at different speeds through different media. Water slows light down more than air, for instance. Corn syrup slows it down even more than water. In this experiment, we create a gradient solution of sugar water in a tank. As a laser beam travels through the liquid, the changing concentration bends its path!

The solution at the bottom of the tank is about 80 percent sugar by volume. As a siphon slowly transfers liquid into the aquarium, we add more and more water to the top container, diluting the mixture. The last layers to be added contain almost no sugar.

dripdripgif

Sugar water is denser than pure water. This property keeps the heavier, more concentrated solution on the bottom of the tank. Lighter mixtures float above in order of density. We chose a siphon system to stack our liquids because it transfers the fluid slowly and gently, without creating too much turbulence. This method allows a relatively smooth density gradient to form.

Our variable solution of sugar water also has a gradient index of refraction, meaning that light travels faster in some parts than others. Namely, light is slowed down the most in the heavy 80% region towards the bottom. It travels faster as the mixture becomes more dilute near the top of the volume of fluid.

laserbend

Imagine a line of children holding hands and running across a field. If they all run at the same speed, the line stays straight. What happens if they’re not all identical athletes, and you place them in order of running speed? The line bends. One end of the chain ends up ahead of the other. This is a bit like what we’ve done to the laser beam.

Written By: Caela Barry

How To Trap a Laser

Ever notice how, when you look into rippling water, you see slices of what’s below the surface mixed with broken reflections of the world above? When light hits a boundary between two different tirUFLmedia, it can either travel ahead into the second medium (refraction), bounce back into the first (reflection), or do a little of both. What actually happens depends on what it’s traveling through and into and the incident angle of the light rays. (Diagram at left courtesy of the University of Florida.)

Light travels fastest in a vacuum. It propagates more slowly (although still incredibly fast) in substances like air and water. The more optically dense a medium is, the slower light travels through it.

Picture a beam of light hitting a boundary from the slower or more optically dense side, e.g. traveling through water towards air. Sometimes, depending on the angle of incidence, the light bounces back completely instead of transitioning into the faster medium. In this situation, the image from underwater never reaches the eyes of an observer above the surface. The information is completely trapped within the slower medium. This is called total internal reflection, and it’s everywhere.

Mirage

A mirage is an example of total internal reflection in nature. Photo by Brocken Inaglory.

If you’ve ever seen the illusion of a puddle of water on the road on a hot day, you’ve experienced total internal reflection in nature. Hot air near the ground is less optically dense than the cooler air above, so light travels faster through it. Rays of sunlight that approach the ground from a certain range of angles bend up and away as they near the surface of the road, carrying the image of the sky– which looks like water– to your eyes!

Humans take advantage of total internal reflection, too. Fiber optic cables shuttle electromagnetic information all over the world. Endoscopes use fiber optic technology to provide a non-surgical window into the human body.

WaterOpticsGif

The stream of water in this experiment partially traps a laser, making it a not-so-great fiber optic cable. The laser signal isn’t completely transmitted from end to end; some light is lost through the sides as the stream becomes turbulent. Escaping light gives the stream a bright green glow.

Try this at home by drilling a hole near the bottom of a clear container, filling it with water, and shining a small laser straight through the container and into the exiting stream!

Written By: Caela Barry

Why Is The Sky Blue?

Ever heard that the sky is blue because it’s reflecting Earth’s water? It’s a myth! If the sky was just mirroring the planet below, it would be brown in Utah. The real reason for our atmosphere’s hue has its roots in a more fundamental question: how do we see the world around us?

Spectrum

The electromagnetic spectrum. Credit: Florida Atlantic University

Human eyes are living light detectors. Color is just our brain’s code for incoming energy level. We call the most energetic light we can see “purple” and the least energetic “red”.

Our built-in biological cameras have a quirk: when confronted with a mixture of colors all at once, they’re overstimulated. Our eyes can’t resolve a blend of energy levels into individual signals, so our visual processing system defines a new category, which we call “white”. The sun’s radiation appears white before it reaches Earth, but it’s really a combination of many colors.

SunFromISS

The sun & Earth as seen from the ISS. Since sunlight hasn’t been scattered by the atmosphere on its way to the camera, it appears white. Credit: NASA

As white sunlight enters the atmosphere, the transition from empty space to air affects each of its components differently. Blue-violet light is bounced around the most drastically by air molecules in its path. From our perspective on Earth’s surface, scattered blue radiation fills the sky. Lower-energy light, which we interpret as the colors red through green, travels more directly downward to our eyes. We interpret this smaller combination — white minus blue-violet — as pale yellow.

Rayleigh-Scattering

Image courtesy of the City University of New York

As sunlight travels farther through the atmosphere, it’s more thoroughly scattered. At sunset, when rays travel sideways through a thick slice of air instead of straight down, we see more of the spectrum spread out across the sky. The leftover light traveling directly to us is mostly red and orange, which explains the sun’s ruddy appearance as it sets.

Screen Shot 2016-05-27 at 10.00.14 AM

Sunset from AstroCamp

Written By: Caela Barry

Survival Skills: Science Style

Light travels incredibly fast. In a vacuum, it speeds along at nearly six trillion miles per hour. Ever notice how your feet look distorted when you wade in the water, or how a straw seems to be cut in half where it enters a full glass? When light travels through a medium, it slows down. When a collection of light rays crosses from one material to another (from water into air, for instance), the change in speed warps the image.

StrawSmall

This warping effect can appear random, as in the case of rippling water, or it can be well-organized. We often take advantage of light’s transition between air and glass, for example, to bend images in a useful way. A magnifying glass works by taking a small image and spreading it out over a large area. What happens when you use it backwards– put a large cross-section of light in, then focus it down to a tiny point?

SunBurn

Try this with the sun as a light source on a warm day, and you’ll find that the visible light and heat at the focus point are intense enough to burn wood!

Written By: Caela Barry

DIY Optics Experiment

Ever tried burning wood or pine needles with a magnifying glass? It works best when you adjust the glass to create a small, bright spot of light. After its 93-million-mile journey to Earth, sunlight isn’t ordinarily hot enough to start a fire, but the magnifying lens focuses a large cross-section of light rays into a single intense point. This kind of lens is called convex.

WaterArrow1

A glass of water is essentially a convex lens. Just like sunlight passing through a magnifying glass, an image traveling through a cylinder of water is focused into a single spot some distance away. The rays don’t stop there, and as they continue, their paths cross. The part of the image that started on the right ends up on the left, and vice versa!

WaterArrow2

This is an easy trick to try at home! All you need is a clear glass or jar and an image to flip. If you don’t see the expected results right away, try putting more distance between yourself and the glass– the image will only appear backwards if you’re past the point where the rays of light meet and cross.

WaterArrow3

A cool astronomical tidbit: Another thing that bends light is gravity. This allows it to focus light as well, and sometimes Earth will be on the receiving end of this. Unlike the fire starting focused sunlight, this is a useful tool that allows scientists to locate black holes and get unique views of faraway objects and is known as gravitational lensing. For a better understanding, check out the animation below:

Gravitational Lensing ESO

Video Source: ESO/Luis Calçada

The ring-like structure of the galaxy in the picture is actually quite common in space. Scientists can’t control when they can see or use gravitational lensing as it is the result of the positions of objects that are very far away, but these serendipitous events allow us to learn more about both of the objects involved!

A_Horseshoe_Einstein_Ring_from_Hubble

In the centre of this image, taken with the NASA/ESA Hubble Space Telescope, is the galaxy cluster SDSS J1038+4849 — and it seems to be smiling. You can make out its two orange eyes and white button nose. In the case of this “happy face”, the two eyes are very bright galaxies and the misleading smile lines are actually arcs caused by an effect known as strong gravitational lensing. Galaxy clusters are the most massive structures in the Universe and exert such a powerful gravitational pull that they warp the spacetime around them and act as cosmic lenses which can magnify, distort and bend the light behind them. This phenomenon, crucial to many of Hubble’s discoveries, can be explained by Einstein’s theory of general relativity. In this special case of gravitational lensing, a ring  — known as an Einstein Ring  — is produced from this bending of light, a consequence of the exact and symmetrical alignment of the source, lens and observer and resulting in the ring-like structure we see here. Hubble has provided astronomers with the tools to probe these massive galaxies and model their lensing effects, allowing us to peer further into the early Universe than ever before. This object was studied by Hubble’s Wide Field and Planetary Camera 2 (WFPC2) and Wide Field Camera 3 (WFC3) as part of a survey of strong lenses. A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Judy Schmidt.

Two gravitational lensing examples captured by Hubble. On the top is a nearly complete Einstein ring. On the bottom, the lensing alignment is slightly off, smearing the images of the distant galaxies to form a friendly smiley face!

Credit: NASA/ESA/Hubble

 

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We would like to thank you for visiting our blog. AstroCamp is a hands-on physical science program with an emphasis on astronomy and space exploration. Our classes and activities are designed to inspire students toward future success in their academic and personal pursuits. This blog is intended to provide you with up-to-date news and information about our camp programs, as well as current science and astronomical happenings. This blog has been created by our staff who have at least a Bachelors Degree in Physics or Astronomy, however it is not uncommon for them to have a Masters Degree or PhD. We encourage you to also follow us on Facebook, Instagram, Google+, Twitter, and Vine to see even more of our interesting science, space and astronomy information. Feel free to leave comments, questions, or share our blog with others. Please visit www.astrocampschool.org for additional information. Happy Reading!

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