20 Minute Labs: The Disappearing Bottle

MAKE A BOTTLE GO INVISIBLE!

Have you ever looked through a glass of water (or maybe a fish bowl!) and noticed how anything behind it looks strange?

That strangeness - also called distortion - happens because light interacts with air and water differently.

Have you ever looked at pencil in a glass of water? Try it! Where pencil enters the water, it looks like it bends at totally different angle.

The bending, or distortion, is due to light refraction. In this month's 20 Minute Lab, we'll play with this scientific concept of refraction to make a bottle inside a glass disappear! Or at least, seem to 😜! 

WHAT YOU'LL NEED

• Jar or large glass
• Narrow glass bottle that fits inside the jar (hot sauce bottles work well!)
• ~6 ounces glycerin, or enough to fill most of the bottle and at least a third of the jar
• Pencil (or anything long and thin for reference)

LET'S GET STARTED!

1. Place the bottle inside the jar
2. Note how you can easily see the entire bottle through the jar.
3. Add glycerin to the bottle so it is filled up to the neck.
4. Then add glycerin to the jar, so it is filled about halfway. (See photos.)
5. Now, look at the jar and bottle straight on. What does the bottom of the bottle look like?
6. Place your pencil behind the jar and move it up and down - note its appearance looking through the jar at different levels.
7. What do you notice?

WHAT'S GOING ON?

You probably noticed that the part of the bottle that was submerged in glycerin seems to have disappeared inside the jar. You probably also noticed that when you held the pencil behind this part of the bottle and jar that it did not look distorted. However, when you moved the pencil up to the a level were there was no glycerin in the jar, it did look bent or distorted.

Why does the bottle seem to virtually disappear? It all has to do with how light behaves.

Rays of light travel at different speeds depending on what they're traveling through. When you turn on a lamp, the light travels from the bulb and through the air at a certain speed. If there happens to be a glass of water nearby, the light travels at a slower speed through the water, and at an even slower speed through the glass itself.

This change of speed causes the light to undergo refraction. Refraction happens when a light wave (like a light ray) changes direction when it enters a new substance/medium.

When you put the bottle into the empty jar, it looked pretty normal, right? But light travels through air at a faster rate than it does through the walls of the glass and bottle. You can easily visual the distortion when you place a pencil behind the jar and bottle.

However, light travels through glass and glycerin at the SAME speed, so when you fill the bottle and jar with glycerin, your eyes perceive no difference. The bottle seems to have become invisible! Even the pencil doesn't appeared distorted or bent behind this area of the bottle.

Can you think of other experiments to try? What happens if you poured glycerin into the jar so it is higher than the level of glycerin in the bottle? What if you used a square vase instead of a round jar? Try it and let us know what happens!

Want to have more fun with your leftover glycerin? Try our 20 Minute Lab: Snow Globes!

SHARE WITH US!

Let us know how your experiments turned out! Share your photos and results with us on Facebook, Twitter, Instagram, or send us an email to info@yellow-scope.com. We love getting your messages!

For more exciting experiments, check out our Yellow Scope science kits on the Shop tab of our website!