fun science light

Quick fact. Ready?
Melatonin is a hormone in charge of regulating one’s circadian rhythm. It is produced naturally by the pineal gland as night time approaches, but this secretion can be disrupted by too much light exposure during the evening hours.

What kind of light? Blue light in particular. This is often given off by electronics such as cell phones, tablets, and televisions.

Found this cool animated gif on the wikipedia page for quantum electrodynamics.

To briefly explain what’s going on: common experience tells you if you shine light on a mirror, light will reflect off at the same angle it reflects on. (In math speak, the angle of incidence equals the angle of reflection). This is true. That’s the result you’ll get if you don’t do any funny business to the mirror. That’s what that final red arrow represents.

But you see, the quantum world doesn’t behave like you might think it does. In fact, to calculate this path, we have to calculate all possible paths the light can take. That’s what all those individual little arrows represent. But because we say a photon (‘light’ = the particle known as a photon) has 'wave-like’ properties, the arrows NOT in the middle cancel each other out!

“Whatever,” you say. “That’s just a bunch of trickery! The light is bouncing from the source, off the center of the mirror, and into the detector (likely your eyeball).”

But it isn’t trickery! These other paths exist! It’s not just a mathematical abstraction.

You see, we could actually, if we wanted to, chop off the center and right of the mirror. If we shone a light on the remaining left from our source, it would not reflect toward point P. I mean, dur right? That’s because the paths are cancelling out. However if we scratch off certain parts of the mirror to avoid this cancelling out, we can actually make the light reflect toward P anyway! In fact, you see this all the time, any time you look at a CD or a DVD for example. This phenomenon (it’s called diffraction) is what causes the light to split into a rainbow.

Just to end, here’s another something to boggle your mind: in QED, a positron is identical to an electron travelling backward in time. In fact, to make accurate calculations, we have to include this possible 'path’ of an electron going backwards in time. If we fail to do so, our calculations are wrong. So, in the lab, when we view a 'positron’ what we’re really seeing is an electron travelling backwards in time.

Placing a test tube into a beaker of glycerol makes it turn invisible! The Glycerol has the same refractive properties as the pyrex glass of the test tube, causing the light to pass straight through without refracting, thus appearing invisible. Learn how to perform this scientific magic trick at home in this video: http://youtu.be/UIovk_LgHRA

What is Refraction?

After I posted about the Total Internal Reflection last week, there were an increasing number of people who wanted refraction and total internal reflection to be explained in layman’s terms. So, this post will cover Refraction and in the posts to come, we will dig deeper.

When light encounters a different medium than the one it is already in, it bends! This phenomenon in physics is known as Refraction.

Which way does it bend?

This is dictated by the Snell’s law, which states that:

a. If light travels from a less dense material to a more dense material the light will bend towards the normal.

b. If light travels from a more dense material to a less dense material the light will bend away from the normal.


Remember this trippy image?

This was the best real world example of Refraction I could ever find on the internet. Due to the refraction of light as it moves from a denser medium ( glass ) to a less denser medium( air ), the image appears to be shifted!

In physics terminology, the image is said to be “Laterally Shifted”.

Hopefully now, you understood what refraction is and what it does.If you have any doubts, feel free to ask.

If you liked this post, do check out:

Physics of invisibility.

Baffling Polymer Balls behavior.

Why is glass transparent?