Are your colors my colors?
Hey Crash, today we're going to talk about sight.
More specifically, how we're able to see and the role light plays in this.
Sight really is a double-edged sword sometimes.
On the bright side, I get to see my reflection every morning.
But then I get to work and I have to look at your ugly mug all day.
It's interesting you mentioned the "bright" side because that's our first clue into
how we're able to see.
Wow you just completely deflected my insult.
Those stress avoidance classes are really working out for you.
In fact, they're the only thing working out for you since you never go to the gym.
Aren't you jealous of my muscles?
Me being jealous of your muscles would be like Eminem being jealous of Justin Bieber's
new haircut.
Speaking of intensely bright things, to understand sight we first have to understand light.
Light is a type of electromagnetic radiation which has a wavelength in the visible spectrum.
Radiation is essentially formed when an atom's electrons drop down an energy level, or orbital,
thus releasing energy.
This energy has both electric and magnetic wave components travelling perpendicular to
one another, making it electromagnetic radiation.
However, this radiation is confusing since it actually has two ways in which it behaves.
I behave in two different ways as well.
There's how I act when Culture is being a little bitch and then there's… well
actually I guess I only behave one way.
What I meant is that light behaves both as a wave and as a particle.
Waves are patterns of energy with amplitude, oscillation and so on like the ones I described
in the "How loud is loud?"
video.
A particle can be thought of as a small portion of matter.
Light was, at first, considered to be a particle by the likes of Isaac Newton.
He observed that shadows had crisp edges and, as such, it only made sense for light to be
matter.
This was despite him also showing that white light could be split into its component colours
by using a glass prism… but we'll come back to colors later.
There were a few physicists who entered evidence into the debate of particle vs. wave but the
case drew on.
Sounds like a court room drama.
"You're out of order!
You're out of order!
The whole trial is out of order GOD DAMN IT!"
Actually that sounds more like a case about entropy… just a little joke for all the
physics kids out there.
Anyway, the next predominant theory came from Scottish physicist James Clerk Maxwell who
pretty much predicted and defined light as an electromagnetic wave in 1864.
His four equations of electromagnetism, which I won't go into today, are the cornerstones
of the field and link electrical fields to magnetic fields.
It wasn't until the end of the 19th century that Albert Einstein revived the "light
as a particle" movement, albeit with a very important caveat.
Einstein believed that the quanta, or smallest particle, of light was the photon.
However, it was the flow of these photons that gave light its wave-like properties.
To examine this further, let's think about two key properties of light: its intensity,
and its energy.
ERGH I didn't realise this was going to be a physics episode.
This is worse than when Family Guy does an episode about Meg.
Jeez where'd you pull that reference from, the mid 2000's?
Just stick with me here.
I liked the part when Peter forgot how to sit down.
That was a good episode.
ANYWAY, Einstein's light quantum theory defined the intensity of light as being proportional
to the amount of photons in a wave.
The actual energy of the wave, however, was equal to its oscillation frequency times Planck's
constant.
The oscillation frequency is how often a photon completes a full cycle of a wave, up and down,
and Planck's constant is a factor connecting these two variables.
In an experimental sense, it had been observed that electrons were ejected from metal surfaces
that were exposed to light.
This phenomenon is known as the Photoelectric effect.
Whether strong or weak light was projected onto metal, however, the energy of ejection
of the resulting electron didn't change.
I'll skip the physics mumbo jumbo but essentially it was expected that if light was a wave then
the electrons energy of ejection would be proportional to the strength of light.
Einstein's explanation of light as a particle solved this quandary and earned him the Nobel
Prize in Physics.
Okay, this is getting ridiculous.
I gotta show the audience this.
So we have cue cards with our lines on them to guide the episode.
And my one now says "Fascinating, but how does this explain the wonders of reflection
and refraction?"
Now I may not be a geek, hell I don't even care about light, but I assure you that no
one, I repeat NO ONE, has ever or would ever say that.
Glad you asked Crash!
Goddammit.
To explore how light interacts with different mediums, it's usually easiest to think of
it as a ray.
Rays are simply thin beams of light that travel in a straight line.
When I say reflection, most of you probably pictured a mirror but all matter reflects
light.
Mirrors are special when compared to other types of matter because their surfaces are
so smooth that any irregularities in the mirror surface are smaller than the wavelength of
light.
Other objects such as rocks for example are too rough and exhibit diffuse reflection whereby
light being reflected is scattered so much as to not "appear" reflective to us.
What property determines how smooth the image in the mirror is?
I'm not sure if it's my perfect haircut, my flawless skin or my rippling abs.
If by rippling abs you mean undulating stomach then sure, let's go with that.
The basic law of reflection is that the angle of the ray reflected is equal to the angle
of the ray incident upon a surface.
By "incident upon", I mean the ray of light which approaches and contacts or intersects
with a surface.
It's a bit like in pool: If you hit a ball against a wall then it will leave the wall
with the same angle.
That's right everyone: It's time for geometry.
I have to admit geometry can be pretty useful.
For example, "What angle does this bullet have to enter Culture's head for him to
stop talking about geometry?"
I won't go into too much detail, I promise.
Let's start with a plane mirror, the type we use every day.
A plane mirror is flat and as such there are a number of properties it carries.
The image in the mirror is always upright, presented at the same distance from the mirror
surface as you are and is at a 1x magnification so you appear normally sized,
Well of course the image is upright; I'm not doing a handstand or something… unless
I'm trying to check out my obliques, of course.
Well not every reflected image is upright.
Take a concave mirror for example: The image appears inverted.
To make sense of reflected images, scientists will often use ray diagrams.
These diagrams project out the expected paths of rays of light based upon the law of reflection.
Using these diagrams one can determine, at least theoretically, the exact position and
orientation of a reflected image.
In the case of spherical mirrors such as concave or convex mirrors, these diagrams become incredibly
useful.
If you have a spoon nearby, go take a look in the concave side of it.
The concave side is the one that curves away from you, the one that carries stuff.
Like cereal or soup or crack cocaine.
WHOA okay I appreciate the assist but let's try to keep this PG shall we?
Culture we both know that we lost any chance of this show being PG when I was appointed
as co-host.
True, but back to the spoon example.
If you look in the concave side of it, you'll notice your image is inverted.
But if you look in the other side, the convex side, then your image is displayed upright.
Imagine yourself as a vertical line facing a large concave mirrored surface.
If you draw a line from the top of your head straight along to the mirror, then the reflected
light will bounce downwards due to the angle of the concave mirror.
Now if you draw a line from your feet to the mirror, we get the opposite effect and the
image is bounced upwards.
In this way, your head and your feet are flipped.
Similar logic can be applied to a convex mirror to explain why your body appears stretched.
In face with enough logic, and patience, any distortion in a mirrored image can be explained.
Okay, okay, enough.
When I said I was interested in reflections I really just meant MY reflection, not all
reflections.
Can we move on?
Fair enough, let's talk about refraction instead!
uuuuuuuuuUUUUUGGHHHHHH!
Refraction is the bending of light we observe when light travels from one medium into the
other.
The main example we'd be familiar with is the distortion of an image in water.
This is due to the differing properties, for example density, between the air and the water.
When we talk about the speed of light, 3 x 108 metres per second, this is actually a
theoretical value indicative of the speed of light in a vacuum.
But when in a medium such as water, both the speed and wavelength of light are altered.
Speed, wavelength and frequency are connected by a simple formula where the speed is equal
to the frequency times the wavelength.
Hence, by using this formula we see that the frequency does not change from one medium
to the other, only the speed and wavelength.
Clearly you and I are not on the same wavelength right now.
Well the importance of this is that when light enters a different medium it is also forced
to change its path, or trajectory, as a result of the differing densities of the two mediums
and subsequent speed change.
Snell's Law is used to describe the angle which light follows when changing mediums
but since Crash is already losing interest as it is I won't get into the sine's and
theta's of the equation.
You guys at home should definitely look into it though!
Just tell me about colors already!
I wanna know why when I trip balls I can see so many colors.
Well colours are essentially just different wavelengths of light.
The electromagnetic spectrum is the full range of possible wavelengths of light and contains
many different types of rays.
Higher wavelengths or lower frequencies include radio waves, microwaves etc. whereas lower
wavelengths or higher frequencies include gamma rays and X-rays.
But between these two ends of the spectrum lies visible light.
Visible light is pretty self-explanatory: It's the light our eyes are able to see
and interpret.
Colors occur at different wavelengths in this region of the spectrum, with red having
a lowest frequency (nearing infrared rays) and violet having the highest frequency (nearing
ultraviolet rays).
White light contains all of these various frequencies and by using a glass prism, as
Isaac Newton did, we can split these frequencies up using the refractive properties of light
discussed earlier!
Wait so you're saying that every single color we see is actually just a tiny fraction
of this whole spectrum..?
Wow that's so… boring.
Oh yeah?
Well are rainbows boring?
Rainbows show the full spectrum of colors ranging from red to orange to yellow to green
to blue to indigo and, finally, to violet.
Rainbows are formed when light refracts and disperses through raindrops.
Imagine each raindrop as a tiny glass prism that separates light into its component colours.
The result is a cone of colors but the cone is cut off by the horizon.
As a result what we see is merely an arc of color.
If we could see infrared and ultraviolet light then the rainbow would also contain these
forms of electromagnetic radiation.
It also says on this site that the rainbow is a sign from God that he will never again
flood the world to destroy all life…
huh.
Try telling that to the people who lost their homes in the Great Mississippi Flood of 1927.
Truly they are a god-fearing people in the south.
So now we know what light is, how do we actually perceive and interpret color?
Well-
Hey come on, this video is gonna go WAY too long!
I have an appointment to get to!
Let's finish this off another time.
Alright, alright.
Next time we'll cover some of the more biological and chemical aspects of sight, detailing the
eye and neural pathways involved in sight.
See you guys next time!
So Crash, what's this appointment about?
Hope everything's okay!
Oh yeah I'm fine, it's just my flexing appointment.
Flexing appointment..?
Yeah, see, like this…
Ooooh yeah, daddy like.
Ergh gross.
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