Did you ever wish you had Harry Potter's Invisibility cloak?
I certainly did when I read the books and watched the movies. So, do you think you can be invisible?
It all depends....
Step 1: List of Supplies:
Step 2: How Our Eyes See
First, let's talk about how we see (how things become visible to us).
Some facts about how we see:
- Light rays are reflected from a surface in straight lines.
- When light rays hit a smooth surface, the light rays are reflected back at you.
- When those light rays enter our eyes and hit our retinas, an image is formed (upside down).
- When light rays hit an uneven surface, the light rays are scattered.
- The reflected light bounces off in all directions, unable to form a coherent image.
Step 3: Reflected Image
Do you see the light colored blob in the bottom of her eye? That's me, reflected in her eye. Isn't it amazing?
So, how do we achieve invisibility in Real Life?
How about a stealth fighter plane/helicopter/ship?
- As the radar antenna turns, it emits extremely short bursts of radio waves, called pulses.
- The pulses move through the atmosphere almost at the speed of light. By recording the direction in which the antenna was pointed, the direction of the target is known. The better the target is at reflecting radio waves, the better it will be able to attain invisibility.
- Stealth technology cannot make the aircraft invisible to enemy or friendly radar. All it can do is to reduce the detection range of an aircraft. This is similar to the camouflage tactics used by soldiers in jungle warfare. Unless the soldier comes near you, you can't see him.
- Reduce radar cross section.
- Change vehicle shape to reflect radio waves in all directions.
- Use new technology to absorb/trap radar waves.
- Use of non-metallic airframe.
Step 4: A Simple Experiment on Invisibility
For this experiment, you'll need large piece of foil (large enough to see your face in).
- Be careful to cut/tear that piece of foil without crinkling it at all.
- Smooth it out (don't touch it too much) and look at yourself in the foil. Sure. It's not like a mirror, but you should be able to make out your facial features.
- Now, crumple that sheet of foil into a fist-sized ball.
- Then, open it up and smooth it out as well as you can.
Now, can you see yourself in the foil? You can't.
So, why do you think you can't see yourself at all in the same sheet of foil?
Step 5: Reflected Light Rays
When the light rays are reflected, the lens of your eyes can focus and form a coherent image (1st picture).
When the foil is scrunchy and rough, the reflected light bounces off in all directions, away from the object (2nd picture). And because these reflected rays are going off in all directions, the lens of your eyes cannot form a coherent image. And that's why you can't see the image.
This is a very simple experiment, but there's a lot to learn from it. For deeper learning, search for pictures of stealth planes, stealth helicopters, stealth ships, etc. There are a lot of angles on the vehicles. Not smooth like the traditional vehicles.
For more information, please check out Kto6Science blog.
Have a great day!